Systems and methods for pedicle screw stabilization of spinal vertebrae

ABSTRACT

The present application is directed to various spinal stabilization systems. The systems can include one or more guiding elements attached to screw members to assist in guiding rod implants and tools to desired locations within a patient. The guiding elements can include a plurality of wires, blades, or tabs. The guiding elements can be capable of criss-crossing or intersecting at or near an incision, such that only a single incision may be needed to perform a surgery. The guiding elements can also include telescoping features that allow the height of the guiding elements to be adjusted in use, thereby allowing multiple telescoping guiding elements to be used with the same incision.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

Any and all applications for which a foreign or domestic priority claimis identified in the Application Data Sheet as filed with the presentapplication are hereby incorporated by reference under 37 CFR 1.57.

BACKGROUND Field of the Invention

The present invention relates to medical devices, systems and methodsfor bone fixation. Specifically, embodiments of the invention arerelated to stabilizing adjoining vertebrae in the cervical, thoracic,and lumbosacral spine. In addition, embodiments of the invention arerelated to fusion or stabilization of vertebrae in the lumbar spine toalleviate axial back pain. Embodiments of the invention are also relatedto improving minimally invasive surgical (MIS) approaches to pediclescrew fusion by reducing the number and size of incisions and the sizeof the medical instruments inserted therein.

Description of the Related Art

While some lower back conditions can be ameliorated with non-surgicalapproaches, spinal fusion is recommended for certain conditions whennon-surgical approaches fail. Non-surgical approaches includemedications, physical therapy, chiropractic treatment, traction,epidural steroid injections, facet blocks or rhizotomy, weight loss,smoking cession, and acupuncture. Conditions that commonly serve asindications for spinal fusion or stabilization surgery can be dividedgenerally into three categories: (i) trauma induced, (ii) curvature, and(iii) degenerative.

Trauma induced conditions include fractures and ligamentous injuries.Fractures typically result from an unfortunate incident involving anextraneous force or fall but may also arise from pathologic conditions,such as cancer or osteoporosis. Fractures are often compressive innature and typically lead to a pathological curving of the spineresulting in a loss of the natural lordotic curvature in the lumbar andcervical spine, known as kyphosis. Fractures of the spine also occurwith translational or rotational forces perpendicular to the axis of thespine. These forces result in fractures of the facet or parsinterarticularis (pars). If the external forces are large enough,vertebrae can collapse resulting in a burst fracture that can injure all3 columns of the vertebrae (anterior, middle, and posterior columns).Many traumatic injuries can heal without surgery, but unstable injuriesthat pose a risk for neurologic injury and/or pain require stabilizationthrough a procedure such as fusion.

A condition called spondylolisthesis characterized by slippage of thespine bones or vertebrae relative to one another can result fromfractures of the pars interarticularis (pars fracture) known asspondylolysis. Spondylolisthesis can also develop from malformation ofthe facet joints by degenerative arthritis as well as congenitalmalformation and pathologic conditions such as tumors. If the pars onboth sides are fractured, then the spinous process and lamina areessentially completely disconnected from the pedicle and vertebral body.This large fragment is called the Gill body. Pars fractures are actuallycommon in people of all ages (often acquired in the teenage years).While, many of these patients are mildly symptomatic and do not requiresurgery, those with progressive symptoms may require surgicaldecompression with or without fusion. Spondylolisthesis results inmisalignment of the spine and increases the risk of a nerve becomingentrapped. Nerves travel within the spinal canal bounded by thevertebrae and their roots protrude from the curved openings in the sidesof the vertebrae called foramina (singular is foramen). These spinalnerves are suspected to be the source of back and radicular pain whenthey become entrapped or when the nerve endings become irritated byirregular or abrasive motion around a disc, bone, or joint.Spondylolisthesis can also aggravate or be accompanied by degenerationof disc or facet joint which can lead to axial back pain.

The normal curvature of the lumbar and cervical spine is lordosis, wherethe posterior aspect of these spinal levels forms a concave curve. Thethoracic spine normally has a kyphotic or convex curve. Curvatureconditions include straightening of the natural curvature as well asabnormal lordosis, abnormal kyphosis or lateral/ rotational bendingcalled scoliosis. Curvature conditions can occur idiopathically duringadolescence, e.g., adolescent idiopathic scoliosis, or develop as asecondary problem in situations where spinal muscle activation isabnormal such as cerebral palsy, spina bifida, or tethered cordsyndrome. Abnormal spinal curvature is common in spinal degenerationwhen the discs and joints degenerate asymmetrically leading to aprogressive curvature (scoliosis, kyphosis, or lordosis) as thebiomechanics of the spine are disrupted. Curvature conditions also occurafter trauma with compression or burst fractures or with ligamentousinjury. Additionally, curvature conditions can occur iatrogenicallyafter previous spinal surgery where the anatomy and biomechanics of thespine have been altered. Such situations include the removal of theposterior tension band after laminectomy as well as the alteration ofphysiologic movement after spinal fusion leading to adjacent levelcompensation and degeneration. Curvature conditions lead to abnormalbiomechanical stress on the discs and facet joints accompanied bycompensatory measures such as facet or ligamentous hypertrophy. Patientscan develop both axial back pain and radicular pain. In patients whohave failed conservative therapy and bracing, surgery can be effective.Surgery in these conditions includes decompression of nerve or spinalcord compression as well as fusion or stabilization. Curvature can becorrected through surgery, and fusion prevents further curvature fromdeveloping.

Degenerative conditions include spinal arthritis and recurrent discherniation. Spinal arthritis is the most common indication for fusionand may exist in the form of severe disc degeneration (also calledDegenerative Disc Disease, DDD) or facet disease. Degenerative arthritiscan also be a cause of spondylolisthesis in addition to traumaticfractures discussed above. Degenerative conditions are generallyaccompanied by nerve compression causing radicular pain in thedistribution of the nerve's receptive field, which usually correlateswith and is manifested in arm or leg pain. Pure nerve compressionsyndromes such as herniated nucleus pulposus (herniated discs) orforaminal stenosis (narrowing of the side foramina canals through whichthe nerves pass) can often be treated with decompression without fusion.Pure disc degeneration syndromes can be treated with fusion withoutdecompression of the nerves. However, most commonly disc degenerationoccurs in combination with nerve compression causing both axial backpain and radicular limb pain. In these circumstances fusion surgery iscombined with nerve decompression surgery.

Fusion functions to eliminate motion in the disc space and facet jointsbetween adjacent vertebrae. The vertebrae provide the rigid structuralframework of the spine and the fibrocartilaginous disc space acts as acushion or shock-absorber. Degradation of the disc space can distortalignment and alter the biomechanical cushion that the disc affords theadjacent vertebrae. This degradation alters the forces impacted upon thevertebrae and results in axial back pain. Fusion is designed toeliminate movement between adjacent vertebrae by either forming a solidbridge of bone across the disk space and/ or creating new bone formationin the posterolateral space to provide stabilization, rigidity, andstrength. Sometimes fusion involves a bone graft taken from anotherlocation in the body (e.g., autograft from the iliac crest in thepelvis) or from an external source, e.g., allograft. Physicians commonlyrefer to the level of a fusion. A single level fusion involvesstabilizing the two vertebral bones adjacent to a diseased disc. Atwo-level fusion involves stabilizing three adjacent vertebral bonesspanning two problematic disc spaces. Each vertebra makes contacts(joints) with adjacent vertebrae at three points, the paired facetjoints located posteriorly and the intervertebral disc locatedanteriorly. Thus, lumbar fusion can be directed either at the posteriorfacet joints or at the anterior interbody/ disc space or both. When ananterior interbody fusion is performed in combination with posteriorfusion, the procedure is termed 360° fusion. One commonly used techniqueof posterolateral fusion is pedicle screw fusion where screws aredirected into the pedicle portions and the bodies of adjacent vertebraeand then rods are connected to the screws across the disc spaces. Thescrews and rods hold the adjacent vertebrae motionless relative to oneanother and allow the bone graft that is placed either in the interbody(disc) space or in the posterolateral space to grow into solid bone.Conventional pedicle screws and rods are metal, typically titanium (Ti)alloy but have been made from stainless steel as well. Recently rodshave been made from a minimally flexible polymer calledpolyetheretherketone (PEEK).

Interbody fusion involves placing one or more spacers (typicallypre-loaded with bone graft material) within the interbody (disc) spacebetween bony vertebral bodies after the degenerated disc has beencleaned out and removed. Spacers are made from bone grafts, titanium,carbon fiber, or polymers such as PEEK. Interbody fusion can beperformed through several approaches including: an anterior approach(anterior lumbar interbody fusion, ALIF), a posterior approach(posterior lumber interbody fusion, PLIF, or transforaminal lumbarinterbody fusion, TLIF), or a lateral approach (direct lateral interbodyfusion, DLIF™-Medtronic, or extreme lateral interbody fusion,XLIF™-Nuvasive). The aim of these approaches is to remove thedegenerated disc and replace the disc with material that induces bonyfusion. Alternatively the disc can be replaced with an artificial joint/disc (discussed below). Each of these interbody approaches hasadvantages and disadvantages. Anterior procedures require aretroperitoneal dissection and risk injury to the large blood vesselsanterior to the lumbar vertebrae. Also injury to the nerve plexusanterior to the vertebrae can result in sexual dysfunction. The lateralapproach is promising but is limited to the upper and mid lumbar levels(rostral to L5,S1) because of obstruction by the iliac crest. Theposterior interbody approach is more time consuming and typicallyrequires more muscle dissection and retraction. However, the posteriorapproach allows the placement of the interbody graft, posterior pediclescrew fusion, and decompression of nerves all to occur through theposterior incision(s).

Although anterior and lateral approaches can be performed stand-alone(without posterior instrumentation), many surgeons will back-up orsupplement anterior or lateral interbody fusions by placing pediclescrews posteriorly after the interbody cage or graft has been placed.This 360° fusion limits movement more than just an isolated anterior orposterior fusion, and fusion rates are increased. However in ALIF andlateral interbody (DLIF, XLIF) cases, two sets of incisions are requiredfor a 360° fusion.

The posterior approaches (TLIF and PLIF) allow an interbody fusion,pedicle screw fusion, and neural decompression to be done all throughthe same posterior incision(s). In the TLIF, a single large interbodyspacer is inserted on the side ipsilateral to the patient's symptomaticside after neural decompression is completed. If both sides aresymptomatic then decompression is required on both sides. A PLIF isperformed by placing two interbody spacers, one on each side. Posteriorprocedures may be done according to: (i) an invasive open procedure inwhich a large incision and/or several incisions are made, (ii) apercutaneous approach in which small incisions and/or few incisions aremade, and potentially (iii) an endoscopic approach in which smallincisions are made and all tools and devices are inserted throughportals with visualization provided on an external monitor.

As an alternative to fusion, recent advances in interbody stabilizationhave resulted in the development of artificial disc technology.Artificial discs replace the degenerated discs and allow continuedmotion at the joint. Both cervical and lumbar artificial discs have beendeveloped. Additionally, dynamic stabilization techniques have beendeveloped for the posterior spine. These posterior techniques utilizepedicle screws and a dynamic rod. Typically the dynamic rod has amechanism to bend under certain loads or forces, thereby absorbing somestress and strain that is applied to the spine. The advantage of dynamicstabilization is that motion is preserved in the spine. However, thedurability of these systems may be an issue. In fusions, the bone graft(interbody or posterolateral) eventually fuses the vertebrae eliminatingthe need for the spinal instrumentation (screws and rods). However indynamic stabilization, fusion does not occur, so the screws and dynamicrods will always be subjected to the strain and forces of the spine.Over time the possibility of loosening of the pedicle screws ormechanical failure may increase. Sometimes the use of a slightlyflexible rod such as a rod made of PEEK may actually increase fusion byreducing stress shielding. Stress shielding occurs when rigid fusionconstructs shield the vertebral bone in contact with the bone graft fromthe stresses required to form and remodel bone.

Posterior lumber stabilization (fusion and dynamic stabilization)techniques have evolved into minimally invasive approaches because suchminimized exposures reduce patient morbidity and facilitate patients'recovery to function. Blood loss and hospital stays are shorter. Theprocess of performing a minimally invasive pedicle screw fusion is thesame as that for dynamic stabilization and involves two basic parts.First, screws are placed percutaneously through the pedicle into thevertebral body. For minimally invasive systems, cannulated screws areplaced percutaneously over a fluoroscopically (an X-ray that can be seenon a video screen) guided guidance element. Generally, two screws areused on each vertebral body being fused, one on a right side and theother on a left side. The second part of the process involves connectingthe screws with a rod and locking the rod and screws together. Indynamic stabilization, the rod or rod-like device (flexible connector)is bendable, but the process of inserting this bendable rod is the sameas that for fusion. For example, a rod-like device (flexible connector),like a rod, fits within the screw heads, but may also include an element(a shock absorber, a spring, etc.) that allows some motion. Thevariations between different minimally invasive systems mostly arise inthe method of placing the rod and locking the rod with the screwsthrough a minimal incision.

Before the intervertebral body spacer is inserted, the damaged ordegenerated disc within the disc space must be removed. In the TLIFapproach, the disc space is accessed through a facetectomy in which theforamen around the nerve roots is opened with a bone-cutting tool suchas an osteotome or a high speed drill. In the PLIF approach,laminectomies or laminotomies are performed to access the disc space.Both TLIF and PLIF allow for decompression of the spinal thecal sac andthe nerve roots; however, the facetectomy in a TLIF allows the maximumdecompression of the exiting nerve root on that side. With gentleretraction of the thecal sac, the disc space is easily accessed. Thenthe instruments used for clearing out the degenerated disc may beinserted into the disc space to complete the discectomy.

Following removal of the disc, the surgeon should prepare the bonysurfaces, known as the end plates, of the vertebral bodies on each sideof the disc that was removed. Peeling off the end plate with a tool suchas a curette induces bleeding which stimulates healing and assimilationof the bone graft to be inserted into the interbody space. The spacer orcage that is to be inserted is typically constructed of bone, titanium,carbon fiber, or polymers such as PEEK. The spacer is usually hollow orat least porous to accommodate bone graft material therein. Boneinducing protein such as bone morphogenetic protein (BMP) is alsocommonly placed within the spacer. After placing the spacer and bonegraft, the rods may be inserted into the pedicle screws and the screwscan be tightened to lock the rods in place.

Typically the placement of the percutaneous screws is fairly straightforward. The insertion of the rod through the screw heads and locking ofthe rod with the screws are the steps that are currently most difficultthrough a minimal incision. In most of the minimally invasive surgery(MIS) systems used today, a guidance element, such as a wire, is placedpercutaneously under fluoroscopic guidance through the pedicle.Percutaneous cannulated drills and screw taps are inserted over theguidance element/wire to prepare the tract through the pedicle andvertebral body for pedicle screw insertion. Dilating tubes and aguidance tube or a retractor system are often used to dilate and holdopen the path around the guidance element through skin and muscle toreduce injury to muscle and tissue when pedicle screws and insertiontools are inserted. Pedicle screws are inserted over the guidanceelements either with or without passage through a guidancetube/retractor. In order to place the rod and locking assembly into thescrew heads, each screw head is associated with a tower that extendsthrough the skin incision. The tower has to accommodate the rod andlocking assemblies so it is typically larger than the maximum diameterof the screw head. Once the towers are in place, the rod is theninserted through one of a variety of methods. The leading MIS system isSextant™ by Medtronic. In this system, the rod is placed by forming apendulum like mechanism. The two or three towers (for one or two-levelfusion, respectively) are coupled together to align the towers, and therod is swung around through a separate incision superior or inferior tothe towers in a pendulum fashion. Once the rod is swung in place,locking caps are placed through the towers and tightened. Alternatively,most of the other systems insert the rod through one of the towers andthen turn the rod approximately 90° to capture the other screws in theother towers. Inserting the rod through the screw heads in a minimallyinvasive system is done blindly, e.g., without direct visualization ofthe screw head. Thus this process is sometimes tedious and frustrating.

The Sextant™ system and other systems that use towers are hindered byboth the number of incisions required and the size of each incision. Theuse of a separate tower for each screw requires a separate incision foreach tower, or a single incision long enough to accommodate two towers.The Sextant™ system also requires an additional incision for the rod,equaling six incisions (three on each side) for a single level fusionand eight incisions for a two level fusion. The other tower systems thatuse the direct rod insert and turn mechanism still require one incisionfor each screw and each incision has to be larger than the size of atower through which the screws are inserted. Typically, each incision isat least 15mm in length. When the sum of the lengths of all incisions onboth sides are totaled, the total length of the current leadingminimally invasive systems often are longer than the single midlineincision of a traditional “open” approach for a single or two levelpedicle screw fusion.

U.S. Pat. No. 7,306,603 entitled “Device and method for percutaneousplacement of lumbar pedicle screws and connecting rods” by Frank H.Boehm, Jr., et al. and assigned to Innovative Spinal Technologies(Mansfield, MA), the entirety of which is hereby incorporated byreference, discloses a system of connecting a rod to the pedicle screwsusing a pin and recesses within the screw heads. According to thissystem the rod can pivot about a longitudinal axis of the pin between afirst position in which the rod is parallel to the longitudinal axis ofthe screw (e.g., vertically oriented) and a second position in which therod is transverse to that axis in order to bridge screws on adjacentvertebrae. The '603 Patent teaches various guide systems (see FIGS. 5and 6), rod holder systems (see FIGS. 8, 9, 10, and 11), and a rod guidesystem (see FIG. 12) but does not include a sleek, detachable systemamong them. Rather, the systems illustrated are tower-like with ratherbulky dilators (80 and 86 in FIGS. 6 and 8), sheaths (81 in FIG. 6),and/or outer housing (120 in FIGS. 11 and 12).

U.S. Publication No. 2008/0140075 entitled “Press-On Pedicle ScrewAssembly” by Michael D. Ensign and assigned to Alpinespine, LLC(American Fork, Utah), the entirety of which is hereby incorporated byreference, discloses attaching the rod to screw heads indirectly via atulip assembly. The tulip assembly has a housing with an inner diametersmaller than an inner diameter of the screw head such that it is easilypressed into position upon the screw head. The rod is then placed byattaching directly to the tulip assembly after connecting the assemblyto the screw head. The publication mentions using a Kirschner guidanceelement (or K-guidance element) for inserting both the pedicle screwsand the tulip member (see [0030], [0032], and [0045]) but does notdisclose how the rods are guided into position.

U.S. Publication No. 2008/0097457 entitled “Pedicle screw systems andmethods of assembling/installing the same” by David R. Warnick andunassigned, the entirety of which is hereby incorporated by reference,like the '075 Publication, also discloses using a tulip assembly as anintervening means to join a rod to the screws. In this system, ratherthan a press-on locking mechanism, the structure is tightened byrotating an inner member and outer housing of the tulip assemblyrelative to one another.

U.S. Pat. No. 7,179,261 entitled “Percutaneous access devices and boneanchor assemblies” by Christopher W. Sicvol, et al. and assigned toDepuy Spine, Inc., the entirety of which is hereby incorporated byreference, describes one of the several tower systems for placement ofpedicle screws percutaneously. The patent describes a situation wherethe angle of the screws intersect, and the towers may interfere witheach other. This situation is rather typical in the lordotic lumbarspine, especially the lumbo-sacral (L5, S1) junction. In order to solvethis problem, they describe cut-outs in the tubes so that two tubes canintersect. Given that the angles of the vertebrae are variable frompatient to patient and the depth of the vertebrae from the skin is alsohighly variable, the variations on the cutouts would have to benumerous. Additionally, when two tubes intersect at the cutout as shownin FIG. 22B in the '261 Patent, the edges of the cutout of one tubeinterferes or blocks off the lumen of the other tube, and vice versa.This occurs because the muscle and tissue surrounding the tubes willpush the tubes together at the section of the cutouts therebysignificantly reducing the lumen through which the rod and otherelements are inserted. The only way to avoid this interference orblockage of the lumens is to keep the tubes separate which wouldnecessitate a larger incision and would eliminate the need for cutoutsin the first place.

SUMMARY

Embodiments of the present invention are directed towards improvingminimally invasive (optionally adaptable for use with the percutaneousor endoscopic approach) TLIF and PLIF approaches and backing up theALIF, DLIF, and XLIF approaches. TLIF provides several advantagesincluding: (i) stabilization of both the anterior and posterior portionsof the spine through one or more posterior incision(s); (ii) the abilityto fill with bone graft material a greater volume and diversity ofspaces (front disc space with the spacer, amongst the screws and rods onthe sides, and in the back of vertebrae) increasing the chances of asuccessful stabilization through the development and solidification ofbone; (iii) the spacer placed within the front disc space maintains thenatural interbody disc height to reduce pressure on nerve roots (frombone spurs, thickened, ligaments, etc.); and (iv) enhanced safetybecause the spinal canal is accessed from one side only and this reducesthe risk of pinching, stretching, or otherwise agitating the spinalnerves.

Embodiments of the invention provide a system, device and/or method(referred to herein as the Microfusion™ system) for performing aminimally invasive posterior and/or transforaminal lumbar pedicle screwfusion or stabilization procedure. Hereinafter references to “fusion”implicitly include stabilization which offers somewhat greater motionshort of completely fusing the bone. Likewise, hereinafter references to“stabilization” implicitly include fusion. The main situations in whicha surgeon can use the Microfusion™ system are similar to the situationsin which the Sextant™ system from Medtronic is used. These situationsinclude a minimally invasive TLIF procedure with either: (i) amicro-lumbar interbody fusion, MLIF™, or (ii) mini-open TLIF on thesymptomatic side to decompress the neural compression, and a pediclescrew fusion through a minimally invasive incision on the contralateralside. Similarly the Microfusion™ system herein would be used bilaterallyin a PLIF approach with the decompression and interbody spacer placementperformed bilaterally. Alternatively, the Microfusion™ system is idealfor “backing up” (with a minimal posterior incision) anterior interbodyfusions (ALIF) and lateral interbody fusions (XLIF™ and DLIF™). MLIF™collectively encompasses (i) transforaminal lumbar interbody fusions andstabilizations, (ii) posterior lumbar interbody fusions andstabilizations, (iii) anterior lumbar interbody fusions andstabilizations, and (iv) lateral lumbar interbody fusions andstabilizations through a minimally invasive “micro” approach using theguidance system described herein. Since the lateral fusions are trulyminimally invasive, a minimal posterior incision for pedicle screwfusion would be very complementary. Lateral interbody fusions arebecoming more popular and more spine companies are coming out with theirown lateral interbody fusion systems. It will be appreciated thatalthough certain embodiments described herein are directed to minimallyinvasive procedures through a single skin incision, the systems andmethods may also be used in open surgery or mini-open procedures throughopenings in the skin of a patient as desired by the practicing surgeon.

The lumbar spine has a lordotic curvature such that the lowest levels,L4, L5 and S1, have a posteriorly concave orientation or alignment,while the upper levels, L1-L3, are less lordotic. This curvature sets upa unique situation in which the trajectories through the pedicles (thetrajectories to insert the pedicle screws) from L2 to S1 are notparallel. Rather, the trajectories commonly intersect at a point aroundthe level of the skin. This configuration is similar to the spokes of awheel in which the spokes (trajectories) meet at a common center point(a hub). Given that many patients have such a lordotic configuration ofthe lumbar spine, it is possible to insert pedicle screws through asingle incision centered in the middle of the lumbar curvature. However,if each screw required a separate tower (or tube) (as in conventionaltower/tube systems) in order for multiple screws to existsimultaneously, then the sum cross sectional area of the towers/tubesdoes not permit a single small incision. The towers/tubes interfere witheach other and get in the way of one another due to their size.

An alternative method is necessary in order to minimize the number andsize of incisions. Reducing the number and size of incisions minimizesthe tissue trauma needed to place pedicle screws for lumbarstabilization or fusion. An ideal system and procedure would take fulladvantage of the natural curvature of the lumbar spine in order toprovide this reduction. However, the apparatuses and methods of thepresent application described and claimed herein are not limited toapplications in the lumbar vertebrae and may also find use for fusing,stabilizing, or otherwise treating vertebrae in other regions of thespine.

The number of osteoporotic spinal patients requiring surgicalintervention is increasing. Historically this complex group of patientshas had complications with bone-screw fixation due to the nature of thebone and types and projection geometries of the screws used, along withtheir methods of insertion. These complications include implant failure,screw loosening and pullout. Recent research suggests new corticalscrews that project in an anteromediolateral direction have advantagesover traditional screws projecting in an anteromedial direction.Embodiments of the present invention take this research into account andcan be used in guiding and placing new cortical screws to project in ananteromediolateral direction in order to overcome many problems oftraditional screws in osteoporotic patients. Further, embodiments of thepresent invention can be used to place multiple new cortical screwsthrough a single incision, minimizing trauma to already sensitiveosteoporotic patients.

One objective of certain embodiments the present invention is to providea simple method and associated apparatus to place two or more pediclescrews through one small hole. This provides a better cosmetic andfunctional result with just a single skin incision of small size(approximately 0.5 to 4 cm in length, approximately 0.5 to 3 cm inlength, or approximately 1 to 2 cm in length) regardless of the numberof screws used. In one embodiment, the single incision is smaller thanthe sum of the maximum widths of two respective largest elements foreach screw that is inserted through the single incision, where anelement includes the screw, screw head, rod, locking assembly andassociated tools.

Another objective of certain embodiments of the present invention is tobe able to insert, position, and manipulate a spinal implant such as arod and a locking assembly through the same small incision in order tolock the rod within the screws. Certain embodiments provide novel waysto insert a rod into the heads of pedicle screws and ways to lock therod within the screws through a single small incision. The systems andmethods involve in certain embodiments the attachment of one or moreflexible wires, flexible yet firm extended blades or extended tabs toeach pedicle screw head to be used to guide the rod down to the screw.By using flexible and strong guidance (or guide) elements that do notcompletely enclose the guided element, the towers/tubes currently usedwith each screw are not needed. The guide elements are configured sothat they can overlap or intersect at or below the skin incision,thereby enabling the use of a small, single skin incision. The screws,rods, and locking assemblies can all be placed through a single smallincision and yet still be appropriately interconnected within because ofthe natural lordotic curvature of the lumbar spine. By attaching atleast one guidance element on each side of the screw head, the guidanceelements assist to align the screw head. The guidance elements also trapor restrict displacement of the rod, forcing it to fit between them anddirectly into the screw head.

Compared to U.S. Pat. No. 7,179,261 to Sicvol described above,embodiments of the present invention eliminate the need for “cut-outs”where the guide elements intersect. For example, in embodimentsutilizing extended tabs or blades, these extended tabs or blades do nothave a proximal, distal, or any lumen, and the configuration of guidanceelements (extended tabs or blades) for screws at adjacent levels allowthe tabs to intersect and overlap completely for any patient with anyrelative geometries. Thus interference between adjacent guidanceelements on adjacent vertebrae is not a problem. Also, in the cut-outtubes taught by the '261 Patent, a rod or other element would still haveto be inserted through the tube at some point. The cut-out tubes requirethat the rod (or other inserted element) is oriented longitudinallyparallel to the long axis of the tube as it is directed into the bodyuntil it reaches a section with side wall openings or slots distal tothe cut-out section, at which point it may optionally be turnedperpendicularly to the long axis and directed out of the side wallthrough the opening or slot. In embodiments of the present invention byusing guidance elements such as extended blades or extended tabs (fromthe screw head), the element that is guided by them and inserted alongthem (e.g., a rod, a locking assembly etc.) does not have to be insertedthrough any lumen. When a rod is inserted using the blades, the bladescan simply be fed through the outer edges of the rod body, through aretaining element or clasp attached to the rod body, or between theouter edges of the rod body and a retaining element (retention thread).Thus, it is possible for the inserted rod or other elements to beoriented perpendicular to the long axis or oriented in any other manneror at any angle during the entire entry pathway. This provides greaterflexibility for avoiding interference between adjacent stabilizationsystem pieces and eliminates the need for a surgeon to identify thecut-out sections before turning the screw/rod perpendicularly and/orreorienting it. Furthermore, since there are no lumens proximally ordistally with the extended tabs, blades from adjacent levels may overlapand intersect without the need for cutout therefore allowing all bladesto exit a single small minimal incision.

The guidance elements can also be used to guide the locking assembliesdown to the screw heads for embodiments in which the locking assembly isnot part of the screw head itself (and already down there). In suchembodiments, guidance is not needed for the locking assembly because itis built into or part of the screw head. Examples of this lattersituation are a hinged door over the rod that swings and snaps intoposition to hold the rod in place in the screw head. In this situationthe built-in locking assembly (on the screw head) is inserted into thepedicle contemporaneously with the screw.

In an embodiment, the locking assembly is also guided down to the screwby small loops placed on the sides of the insertion tools or small holesor slots made in the sides of the insertion tools. The guidance elements(e.g., wires, extended blades or extended tabs) pass through theseloops/holes (the loops pass over the guidance elements) to guide theinsertion tools down to the screws to deposit (e.g., drop off or detach)the rods and locking means. In another embodiment, the locking assemblyis guided down to the screw by a notched lock and glide mechanismbetween the locking assembly and the guidance element such as extendedblades or tabs. The notched groove on the extended blades traps thelocking mechanism into position allowing it to only slide down the bladeto fit perfectly into the screw head. Due to the flexibility of theguidance elements, coupled with their ability to possess a high strengthwhile occupying a small volume, several of them can coexistsimultaneously even in a small incision. Furthermore, guidance elementsthat are less flexible or made of rigid or semi-rigid materials such asblades or extended tabs can be offset from one pedicle screw to theother. This offset advantageously allows the blades to intersect andcriss-cross while still allowing the rod and locking mechanism to beplaced.

According to one embodiment, the locking assembly is part of the screwhead itself and is therefore deposited when the screw is placed, beforethe rod arrives, rather than requiring separate guidance and beingplaced after the rod. For example, the locking assembly (i) may involveturning the screw head to trap the rod and/or (ii) may include elementsthat snap into place to trap the rod and/or (iii) may include a carvedout channel for the rod in the body of the screw head that restricts itsmotion. According to these embodiments, respectively, the rod may beunlocked, provisionally locked (restrained), or securely lockeddepending upon (i) the extent or angle of rotation of the screw headabout an axis, (ii) the length of extension or extent of flexion forprotruding elements that snap into place, and (iii) the position of therod inside grooves of the screw head. The screw head also might haveretaining elements including bars, barbs, teeth, balls, etc. thatprotrude upon activation to trap the rod (or other elements insertedinto the screw head) by covering a top surface of the rod and/or matingwith the rod's peripheral edges to enclose upon it and stabilize itthrough friction or physical pressure. This embodiment encompassesmodern capless locking assemblies and those without set screws.

Another embodiment is a hybrid system where each screw is placed throughshort towers or tubes that do not come to the skin surface. Wires, bladeor tab extensions are attached to the top of the towers or tubes so thatthe screw, rod, locking assembly, and tools used for insertion,adjustment, locking, compression, distraction, and removal are guided bythe extensions close to the skin but through individual towers or tubesclose to the bone and pedicle screw. This hybrid system offers both theadvantages of the wires/extended blades/tabs in which many guidanceelements can overlap in a single incision at the skin level and theadvantages of a tower or tube system are preserved at the bone level.Some surgeons who are comfortable with the tower system but who want theadvantages of the blade/tab system may want to use this hybrid system.

In one embodiment, the towers, tubes, blades, arms, or other upwardlydirected extended guidance elements may comprise adjustable heightguiding elements, such as telescoping or telescopic guiding elements. Insome embodiments, the telescoping guiding elements are advantageouslyconnected to wires or other upwardly directed extension elements(blades, tabs, etc.) that permit the guiding elements to be telescopedto a smaller height and for example be positioned entirely below theskin incision. The wires or other upwardly directed extension elementsadvantageously maintain connection with the telescoping elements tocontrol and or retrieve the telescoping elements. Two or more sets oftelescopic guiding elements attached to respective screwed can createoffset, intersecting paths during a minimally invasive surgery to guideimplants or tools. The telescoping towers, tubes, blades, arms, orextended tabs get out of the way of other towers, tubes, blades, arms,or tabs by adjusting the height of the telescoping guiding elements.Pieces of the towers, tubes, blades, arms, or extended tabs can be slidout of the wound as long as they are guided by extension wires orstring.

Making some of the guidance elements telescopic allows for more guidanceelements to fit through a single incision smoothly, therebyadvantageously reducing the need to have a larger incision and/ormultiple incisions. After insertion, the various guidance elements maybe deployed telescopically as needed. Using telescoping components aspart of the upwardly directed extended guidance elements allows a rodfor stabilizing vertebrae to be inserted into the body through thetelescoping components and through the same singular incision,minimizing invasiveness of the procedure.

A number of other embodiments may achieve the same desired effect astelescoping the height of each tube. For multiple tubes to be placedthrough a single incision, all of the tubes except or even including theone extending through the incision may be shortened. Thus, in oneembodiment the height may be adjusted either by telescoping or byshortening the tube, blade or other component. The shortening processcan alternatively occur by cutting material amenable to cutting such asplastic or metal. Additionally some material could be cut by melting orcauterizing. Another embodiment is merely bending a flexible part of theguidance element away from the path of the other screws and towers, suchas described in U.S. Pat. No. 7,846,093, U.S. Publication No.2008/0262318 A1 and U.S. Publication No. 2009/0222044 A1, the entiretyof each of which is hereby incorporated by reference. In someembodiments, guidance elements can have a multitude of flexibleconsistencies such that the guidance elements are more firm or rigidthrough the muscle and fascia which places a significant force upon theguidance element. Above the fascia, the forces are lessened due to thepreponderance of fatty subcutaneous tissue. Thus in the region of thesubcutaneous tissue and skin, it is beneficial to have more flexiblecomponents that can also bend out of the way of other trajectories forscrews. The greater flexibility at the skin level also provides lesspressure on the skin and will lead to less damage to the skin which isbeneficial for healing.

The height of the guidance elements can also be adjusted by snapping offportions at pre-scored intervals along the elements. Extended tab screwsmay be pre-scored to break off or snap off after the rod has been lockedinto the screw head. A guidance element that has been pre-scored in asimilar fashion at 1-5 mm intervals along the entire extended tab ortube would allow the height of the blade or tube to be customized foreach patient. Alternatively, the guidance elements could be comprised ofa multitude of sub-units that lock together to make one guidanceelements. More complex and sturdy locking mechanisms could easily beenvisioned and are within the scope of the current invention. The heightof guidance elements can also be adjusted by an accordion typemechanism. Similarly Chinese lanterns and mini-blinds also demonstrateeveryday examples of mechanisms in which the height can be adjusted. Acoiled flexible guidance element configured in a spiral or spring shapecan also allow adjustment in height by stretching or collapsing thespring. Furthermore, such a spring mechanism allows other items such asscrews to be placed through the spring by spreading the coils of thespring at the skin incision to allow the other screws, rods, lockingmechanisms, etc. to be placed through the spring mechanism.

All combinations and arrangements of towers, tubes, blades, arms, tabs,wires, and other upwardly directed extended guidance elements, either asdescribed herein or in hybrid systems which combine conventionaltower/guidance elements as described in the prior art (such as describedin the references incorporated by reference throughout thisspecification) are contemplated as within the spirit and scope of thepresent invention. As used herein, the term guiding or guidance elementis intended to include one or more components extending between a screwand a skin incision, preferably directly or indirectly coupled ordetachably connected to a screw head, and includes both conventionaltowers or tubes such as those made of rigid or semi-rigid materials asdescribed in the patents and publications incorporated by referencethroughout this specification, as well as the additional embodiments ofguiding or guidance elements as described herein. The most suitableselection and arrangement is for the surgeon to determine in eachparticular case. For example, in one embodiment, there may betelescoping tubes at one level, wires at the next level, and blades atthe next level on one side (of the slot for the rod) with bladesattached to wires on the other side (of the slot for the rod). Differentvariations may be selected for each side (medial, lateral) in order tointroduce more components through the same incision. The goal is toprovide enough guidance elements to properly guide the stabilizationrods, locking assemblies, tools, etc. to the pedicle while minimizingthe number of incisions and preventing overcrowding Eliminatingovercrowding permits proper visualization so that the surgeon can workcomfortably and efficiently.

A further objective of embodiments of the present invention is to reducepatient discomfort and the potential for iatrogenic injury. Providing asystem and method designed for use through a single incision assiststhis purpose. Only one quality incision need be made. With everyincision that is made there is at least a small risk of inadvertentinjury, including nerve damage, even by a skilled surgeon. However,incising is not the only risky stage of the procedure, nor the onlystage capable of causing patient trauma yet having the potential forimprovement to reduce these risks and liabilities. Another step of theprocedure commonly causing post-surgical patient discomfort anddiminished motor/sensory function is placement of the rods within thescrews. The extended blades/tabs not only guide the rods to the screwsbut also function to hold nerves and muscles out of the screw head foreasier insertion of the rods and locking assemblies. With nerves andmuscles restrained from entering the trajectories along which the rodsare delivered, there is a reduced risk of pinching, tearing, or severinga nerve or muscle.

While most minimally invasive pedicle screw systems are designed withparallel trajectories for the placement of pedicle screws and theirassociated towers, embodiments of the present invention allow for thepossibility of intersection and near complete overlap of the paths ofthe screws and guidance elements. These embodiments permit the widestflexibility in overlap, intersection and spatial configuration of thepaths of the screws and guidance elements. The smallest skin incisionoccurs when the maximal amount of overlap or intersection occurs at theskin incision. The flexibility of these systems is exhibited by the fullspectrum of permissible embodiments. In certain embodiments, theupwardly directed guide elements (such as guide wires or guide shafts)associated with each of two or more screws extend upward from theirrespective screw heads through one or more skin incisions to form, asidealized lines or cylinders in space, a configuration selected from thegroup consisting of:

-   -   (i) parallel configuration of the guide elements associated with        different screws;    -   (ii) skew configuration where the guide elements associated with        different screws are neither parallel or intersecting;    -   (iii) converging but not intersecting configuration;    -   (iv) intersecting at an inverted “V”-configuration where the        proximal ends intersect outside, at, or below a surface of skin        and at an angle between 0 and 180 degrees;    -   (v) intersecting at a “T” or an inverted “Y” configuration where        a proximal end of the guide element(s) from one screw intersects        the guide element(s) from another screw(s) at a point other than        at an end of the guide element(s) and at an angle between 0 and        180 degrees, where the intersection point is outside, at, or        below a surface of skin;    -   (vi) intersecting at an “X”-configuration or a criss-cross        configuration where guide elements of two or more screws        intersect at points not at the ends of the guidance elements and        at an angle between 0 and 180 degrees, where the intersection        point is outside, at, or below a surface of skin; and    -   (vii) diverging configuration where the proximal ends outside        the skin are farther apart than the distal ends at the screw        head.

In some embodiments, a system is provided for performing spinestabilization through an opening in skin of a patient. The opening mayin one embodiment be a single, minimally invasive skin incision. Thesystem comprises a first screw having a screw head and a first guidingelement comprising adjustable height component detachably connected tothe first screw, the first screw being configured for implantation in afirst vertebra. The system also comprises a second screw having a screwhead and a second guiding element detachably connected to the secondscrew, the second screw configured for implantation in a secondvertebra. The first screw with the first guiding element and the secondscrew with the second guiding element can be delivered into the firstand second vertebra. The adjustable height component of the firstguiding element can be adjustable to reduce a height of the firstguiding element at or below a level of the skin when the first screw isimplanted in the first vertebra to allow the second guiding element toextend through the skin opening when the second screw is implanted inthe second vertebra. In some embodiments, the adjustable heightcomponent comprises telescoping components, and can assume the form of aplurality of cylindrical members and/or a plurality of blades.

In some embodiments, a system is provided for performing spinestabilization through an opening in skin of a patient. The systemcomprises a first screw having a screw head configured to be implantedin a first vertebra and a second screw having a screw head configured tobe implanted in a second vertebra. The system comprises at least one orboth of: (i) a first guiding element detachably connected to the firstscrew configured to have a height at or below a level of the skinopening when the second screw is implanted in the second vertebra, and(ii) one or more flexible wire(s) configured to extend upwardly from thefirst screw and/or from the first guiding element and through the skinopening when the second screw is implanted in the second vertebra. Thesystem further comprises a second guiding element detachably connectedto the second screw, the second guiding element comprising a rigid orsemi-rigid material configured to extend through and above the skinopening when the second screw is implanted in the second vertebra. Aspinal implant member is connectable between the first screw and thesecond screw. Either one or both of the first and second guidingelements can comprise a tube or blades. In addition, either one or bothof the first and second guiding elements can comprise telescopingcomponents.

In some embodiments, a system is provided for performing spinestabilization. The system comprises a first screw having a first screwhead and a second screw having a second screw head. A spinal implant,which may be a rod or a flexible connector, is configured to be coupledto both the first screw head and the second screw head. A first meansfor guiding the spinal implant and/or instruments to the first screw isdirectly or indirectly connected to the first screw. A second means forguiding the spinal implant and/or instruments to the second screw isdirectly or indirectly connected to the second screw. At least one ofthe first and second means for guiding comprises means for permittingthe first screw, second screw and spinal implant to be delivered into apatient through a single, minimally invasive skin incision. In oneembodiment, the minimally invasive skin incision is between 0.5 cm and 4cm, more preferably 3 cm or less or 2 cm or less.

In some embodiments, a method of treating the spine is provided. Themethod comprises making an incision in the skin of a patient to provideaccess to a spinal location; delivering a first screw through theincision and into a first vertebra and second screw through the sameincision and into a second vertebra, wherein at least one of the firstscrew and second screw has detachably connected thereto an adjustableheight guiding element extending upwardly through the incision;delivering a rod or flexible connector to the screws; and locking therod or flexible connector to each of the screws. In some embodiments,wherein both the first screw and the second screw having detachablyconnected thereto a first plurality of telescoping guiding elements anda second plurality of telescoping guiding elements, respectively, themethod further comprises delivering the first screw through the incisionand into the first vertebra with the first plurality of telescopingguiding elements extending through the incision; reducing a height ofthe first plurality of telescoping guiding elements so that an uppermostone of the telescoping guiding elements is positioned below theincision; and delivering the second screw through the same incision intothe second vertebra with the second plurality of telescoping guidingelements extending through the incision.

In some embodiments, a method of treating the spine is provided. Themethod comprises making an incision in the skin of a patient to provideaccess to a spinal location; delivering a first screw through theincision and into a first vertebra, wherein the first screw, afterimplantation, has at least one or both of: (i) a flexible wire extendingupwardly from the first screw and through the incision, and (ii) a firstguiding element detachably connected to the first screw with a height ator below a level of the skin incision; delivering a second screw throughthe same incision and into a second vertebra, wherein the second screwhas detachably connected thereto a second guiding element comprising arigid or semi-rigid material extending through and above the skinincision when the second screw is implanted in the second vertebra;delivering a rod or flexible connector to the screws; and locking therod or flexible connector to each of the screws.

Other objectives and advantages of embodiments of the invention will beset forth in the description which follows. Implicit modifications ofthe present invention based on the explicit descriptions will be, atleast in part, obvious from the description, or may be learned bypractice of the invention. Such subtle, predictable modifications andadaptations are taken to be within the scope of the present invention.Additional advantages of the invention may be realized and obtained bymeans of the instrumentalities and combinations particularly pointed outhereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention, andtogether with the general description given above and the detaileddescription of the embodiments given below, serve to explain theprinciples of the invention.

FIG. 1 shows an embodiment of guidance elements as offset extendedblades/tabs attached to screw heads with the extended blades attached tothe outside of one screw head and the inside of another screw head.

FIGS. 2A and 2B show how the offset extended blades/tabs function inoperation to intersect/cross without interference as the blades/tabsextending from one screw head pass inside/outside the blades/tabsextending from another adjacent screw head such that the two could passthrough the same incision. FIG. 2A is a side view and FIG. 2B is ahead-on perspective view.

FIGS. 3A and 3B show another embodiment in which the extendedblades/tabs have creases and are divided into foldable panels, straightin FIG. 3A and folding to curve slightly in FIG. 3B. Opening the panelspermits the guidance elements to accept the rod, while folding thepanels aids in guiding a locking assembly downward toward the screw headafter the rod has been inserted.

FIG. 4 shows an embodiment for the screw cap locking assembly in which ascrew cap transporter has an extended or protruded portion to engagewith a corresponding recess or slit in a longitudinally extendedguidance element or blade. The screw cap transporter is slid down to fitperfectly on top of the screw head such that the screw cap lockingassembly is screwed out of the transporter and into the head of thepedicle screw.

FIG. 5 shows the screw cap and transporter of FIG. 4 in operation,engaging with the recessed longitudinally extended guidance element, tobe moved downward to the screw seat, from a perspective looking downfrom above.

FIGS. 6A-6C show three additional side views of the screw cap lockingassembly and transporter element, with the protrusion engaging with therecessed guidance element, and also demonstrating (in FIG. 6C) how theextended guidance element and transporter easily detach from the screwhead.

FIGS. 7A and 7B show how the upwardly directed extended guidanceelements for two adjacent screws are offset from one another such thattheir respective locking assemblies (screw caps and transporters withprotrusions) can be guided down to their respective screw headssimultaneously without interference.

FIGS. 8A and 8B show one arrangement at the base of the longitudinallyextended guidance elements in which the guidance elements for one screw(the upper one) are attached to the inside of the screw head, while theelements for the other adjacent screw (the lower one) are attached tothe outside of the screw head, such that one set of guide blades (forthe upper screw) fits completely within an adjacent set of guide blades(for the lower screw). The guidance elements attached to the inside ofthe screw head (the upper one) are close enough to allow the screw capto screw through threads on the blades without a transporter. The widelyspaced guidance elements require a transporter to bring the screw cap tothe screw head.

FIGS. 9A and 9B show another arrangement at the base of thelongitudinally extended guidance elements in which the guidance elementsfor one screw (the upper one) are attached to the right side of thescrew head, while the guidance elements for the other adjacent screw(the lower one) are attached to the left side of the screw head, for aleft-left-right-right offset arrangement of the extended guide bladesfor adjacent screws when intersecting.

FIGS. 10A-10C show an embodiment for the screw cap locking assembly inwhich there is a concentric outer screw holder, threaded on the outsideto engage with corresponding threads on the inside of the extended guideblades, and also threaded on the inside so that the inner screw can beadvanced past the holder, further into the screw seat, upon properpositioning over the screw head.

FIGS. 11A-11C show a pedicle screw with a tapered shaft directeddownwards and with a concave U-shaped screw head and detachableelongated guidance elements directed upwards (one on each side of thehead). The elongated guidance elements may attach directly to the screwhead (left image) or they may attach to 2 or more short guidanceelements on each side of the screw head. This configuration creates aguidance element cage that forces the screw head and the rod to alignwith each other as the rod is lowered into the seat of the screw head.

FIG. 12 shows the pedicle screw being inserted into the pedicle portionof a vertebra on the anatomical right side of the central lamina.

FIG. 13 shows two pedicle screws in position on two adjacent vertebraeon one side of a vertebral column, with the screw shafts buried withinthe vertebral bones and the U-shaped screw heads protruding from thepedicles' surfaces. Also shown is a rod being guided down (at an angle)to the screw heads, between each of two sets of two guidance elements,one for each screw.

FIG. 14 shows the rod in a proper final position fully inserted withinthe screw heads of the pedicle screws in adjacent vertebrae along oneside of a vertebral column for a partial (half-finished, the other sidehaving yet to be stabilized) one-level stabilization. The lockingassemblies are not shown here but may also be guided by the guidanceelements down to the screw heads.

FIG. 15 shows the guidance elements (for guiding the rods, lockingassemblies, etc.) having been detached from the screw heads of thepedicle screws along the anatomical right side of the vertebral column,but with the same screw head-guidance element system still in place onthe anatomical left side of the vertebral column ready to accept andguide a rod down to the pedicle screws. The locking assemblies are notshown.

FIG. 16 shows the second rod in place within the screw heads on theanatomical left side pedicles of the vertebral column, with thedetachable screw head guidance elements remaining on only the anatomicalleft side.

FIG. 17 shows an embodiment in which the rod also has guidance elementsor threads (called rod retention threads) on each side extending betweenits longitudinal ends to form a loop with the body of the rod forsecuring the rod along the screw head guidance elements duringplacement.

FIG. 18 shows the rod with retention threads being directed down to twoscrew heads (one for each longitudinal end of the rod), along screw headguidance elements (corresponding to each side of each pedicle screwhead) inserted through the rod retention loop on each side of the rod.The rod retention threads “trap” the guidance elements so that the endsof the rod cannot be pushed out of the screw head.

FIGS. 19A-19F show an embodiment in which two guidance elements areattached to the top of the screw head, one on each side. Threeorientations (left to right) show the process of lowering the rod intothe screw head guided by the guidance elements (FIGS. 19A-19C) alongwith the final position in which the rod is completely within the screwhead (FIGS. 19D-19F).

FIGS. 20A-20C show a locking assembly being lowered to attach to thescrew head to secure the rod within. An instrument used to lock alocking assembly onto the screw head can also guided by the guidanceelement but is not shown in this diagram.

FIGS. 21A-21F show another embodiment in which the guidance elements areconnected to flexible strands. The strands are then connected to the topof the screw shaft or the base of the screw head. As the rod is loweredinto the screw head, guided by the guidance elements, the flexiblestrands wrap around the rod. Each strand is just long enough(approximately half of the circumference of the rod) to wrap around therod so that the ends of the guidance elements meet together above therod.

FIGS. 22A-22C show how threads can be wrapped around the rod and broughttogether to guide a cannulated locking assembly (e.g., cap) as well asother cannulated tools (not shown) down to the screw head.

FIGS. 23A-23C show the insertion of a longer rod through 4 sets ofguidance elements attached to 4 pedicle screws in a three levelstabilization. The left image shows the guidance elements in a neutral,straight position. The middle and right images show the guidanceelements of the two superior vertebrae (L3 and L4) splayed open so thatthe rod can be easily tunneled in between the guidance elements.

FIGS. 24A-24C show an embodiment using a tool to separate the guidanceelements deep below the skin surface. In this manner, the skin incisionremains small. A “T”-shaped tool with a hinged “T” portion is attachedto the guidance elements and slid partially down towards the screw head.As the hinged “T” is opened, the middle section of the guidance elementsis separated. This opened window allows the rod to be tunneled inbetween the guidance elements, especially in instances where the rod andpedicle screw heads are inserted through separate incisions.

FIGS. 25A-25C show embodiments of inserting a rod through guidanceelements that do not share an incision with the rod. Here the lowest twolevels (L5 and S1) do share a single incision but the upper two levels(L3 and L4) have separate incisions. Rod retention threads only span theinferior half of the rod and only capture the guidance elements of thelower two vertebrae (L5 and S1). The superior end of the rod is thenpushed through the guidance elements of the upper two vertebrae (middlefigure). Or, a thread that is attached to the superior end of the rodcan be used to pull the rod through the guidance elements of the uppertwo vertebrae. This thread can be introduced in between each set ofguidance elements by a large suture needle that is inserted in oneincision and is pulled out of the next incision in between the guidanceelements.

FIGS. 26A-26D show an embodiment of flanged attachments that help therod to find the proper orientation to best fit into the screw head. Asshown, each attachment is preferably convex in a direction towards therod so that as the rod approaches the screw head, the entrance to thescrew head can accept a large range of angles in which the rod isoriented and still receive the rod, gradually improving the rod'sorientation as it gets closer to the seat of the screw head.

FIGS. 27A and 27B show two sequences of lowering a rod into a malalignedscrew head (or, of lowering a malaligned rod into a properly alignedscrew head) using flanged attachments. The bi-convex nature of theflanged attachments permits the rod to twist and adjust as it islowered. Otherwise, without the flanged attachments, in a malalignedsituation the rod would hit the edges of the screw head and would not beable to be lowered further. The flanged attachments are shown here asdetachable elements on the screw head; however, another preferredembodiment is a flanged and convex shaped rod guide built into the topsof opposing sides of the “U” shaped screw head (e.g., may be integrallypart of the screw head interior itself).

FIGS. 28A-28C show another embodiment in which a guidance element isconnected to a screw with break off extended tabs. Extended tabs areused to help reduce the rod into the screw head in cases of malalignmentof the screw heads. Extended tabs are removed by snapping them off afterthe rod is locked in place. A guidance element attached to the extendedtab helps to guide the rod and locking assembly into the screw head. Theguidance element is removed when the extended tab is removed. Extendedtabs that are tapered or triangular in shape also act similarly toflanged attachments to guide a rod into the seat of a malaligned screwhead.

FIGS. 29A-29C show another embodiment in which a guidance element isconnected to a clamp or device that holds the screw head. An embodimentof the clamp or device is composed of at least two parts that can bebroken apart after the rod is locked in place so that the pieces of thedevice can be removed with the guidance element. The clamp or device isattached to the screw before insertion into the bone. The clamp ordevice is shaped so not to impede the placement of the rod into the seatof the screw head. The parts of the clamp are held together by a thinstrand that is cut or snapped apart after the rod is locked in place.The clamp or device is made from metal, polymer, or plastic materialssuch that no residual is left after the clamp is removed.

FIGS. 30A-30D shows an embodiment for the locking assembly in which thescrew head itself forms the locking assembly and no caps or set screwsare needed. In this particular embodiment the screw head can be rotatedto trap the rod.

FIGS. 31A and 31B show various arrangements of guidance elementscomprising telescoping tubes closer to the pedicle and connected towires at the skin level incision. The telescoping tubes go from wider tonarrower along a trajectory extending from the pedicle of the vertebrato the incision.

FIG. 32 shows a rod inserted through a first plurality of telescopictubes being guided out of a first window in a first lowermost tube andinto a second window in a second lowermost tube of a second plurality oftelescopic tubes.

FIG. 33 shows the rod after it has been lowered through the first andsecond windows of the first and second lowermost tubes, respectively,into the first and second screw caps of first and second pedicle screwsof first and second vertebrae.

FIGS. 34A-34D show another embodiment of telescoping guiding elements,this time with telescoping guiding arms configured with an indentationthat creates a groove or channel along the length thereof to receive aprotruding portion of a locking assembly or other element, in order toguide the locking assembly down to the base of the arms, just above therod.

FIGS. 35A-35C show another embodiment of guiding elements wherein anuppermost guiding element may be removed and reinserted through the skinincision. FIG. 35B shows how a portion of the blades that crosses theskin incision can be slid off of flexible wires, allowing the secondscrew to be inserted through the incision with minimal interference.Once the second screw and the second guidance elements are in place, theblades of the first guidance element can be slid back down the wiresinto its original position.

FIGS. 36A-36C show a hybrid embodiment with extended blades or arms onone side of a slot configured to receive a rod and much shorter bladesor arms on the other side. Wires attached to the short blade or arm helpkeep muscle and fascia from interfering with the placement of the rodand locking assembly. This configuration can alternate from one vertebrato the next, as shown, with the longer and shorter blades changingsides.

FIGS. 37A-37D compare drilled hole volumes and relative positions forpedicle screws implanted along a traditional trajectory and according toa new cortical screw trajectory method. (Figures taken from B. G.Santoni, et al (2009) Cortical Bone Trajectory for Lumbar PedicleScrews. The Spine Journal 9:p 366-373, the entirety of which is herebyincorporated by reference).

FIGS. 38A and 38B show side and head-on views of a two-level fusion,which involves stabilizing three adjacent vertebral bones spanning twoproblematic disc spaces, with all guidance elements (wires) on all threevertebrae fitting through a common single incision at skin level usingthe cortical screw technique shown in FIGS. 37A-37D.

FIG. 39 shows different embodiments of a telescoping guiding elementincluding a half-cylinder portion lowered and rotated to adjust theheight and orientation of the guiding element.

FIGS. 40A-40D show different views of the telescoping guiding elementwith the half-cylinder portion lowered to reduce the height of theguiding element. FIG. 40A (left) is the same configuration as FIG. 39with the telescoping extension on the outside of the bottom tube. FIG.40B shows the telescoping extension on the inside of the bottom tube.The half-cylinder extension on the inside has a smaller diameter thanthe extension in FIG. 40A. This size difference is helpful when theblades intermesh when intersecting at a small incision. FIG. 40C showsthat the top of the telescoping extension can be smaller than ahalf-cylinder, while FIG. 40D shows that the top of the telescopingextension can be larger than half-cylinder.

FIG. 41 shows a telescoping guiding element with a half-cylinder portionplaced on a vertebral body.

FIG. 42 shows the telescoping guiding element of FIG. 41 with thehalf-cylinder portion lowered to reduce the height of the guidingelement.

FIG. 43 shows a pair of telescoping guiding elements havinghalf-cylinder portions in use.

FIG. 44 shows a different view of the pair of telescoping guidingelements of FIG. 43 in use.

FIG. 45 shows the pair of telescoping guiding elements of FIG. 43positioned on first and second vertebrae.

FIGS. 46A-46D show embodiments of guiding elements having expandableblades or tabs.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments of the invention involve improved systems, apparatuses andmethods for guiding one or more screws, rods, and locking assembliesdown to the vertebrae and for securing the rod to stabilize thevertebrae. Screws may include pedicle screws as shown in the figures andas described in the patents and publications incorporated by referenceherein, and with reference to FIG. 1 may include a threaded boneengaging shaft 101 and a screw head 102. The threaded shaft 101 may berelatively moveable to different angles relative to the screw head 102.For example, a proximal end of the threaded shaft may include aspherical or semi-spherical head that engages a similarly-shaped seat ina lower portion of the screw head 102. The screw head 102 has generallya U-shape, as shown in FIG. 1, defining upwardly extending arms thatform a channel for receiving a rod 104. The rod may either sit on thehead of the threaded shaft 101, or may sit on an insert placed in thescrew head 102 for receiving the rod 104.

A locking assembly may be built into or attached onto the screw head orbe a separate element. Locking assemblies that are separate elementsinclude (but are not limited to) those reliant on caps and set screws.Locking assemblies integrated with the screw head include (but are notlimited to) rotatable mechanisms in which a turn of the screw head trapsthe rod. The locking assembly may be guided down to the screw before orafter insertion of the rod depending upon the details of the lockingmechanism used to secure the rod. In some cases, the locking assembly isalready present on the screw head before the rod is received. In othercases the rod is inserted into the screw head first and the lockingassembly follows. In one example, the upwardly extending arms of thescrew head 102 may be internally threaded to receive an externallythreaded cap screw that is rotated into the screw head 102 to apply adownward force to a rod 104 sitting in the channel of the screw head.This downward force may also then lock the position of the screw head102 relative to the shaft 104.

The guidance elements for directing the rod, various locking assemblycomponents (e.g., screw head caps), surgical insertion and manipulationtools, and other components into position may be any type of upwardlydirected, extended guidance elements. These guidance elements arepreferably detachably connected to the screw heads or screws so thatthey can be easily removed once a procedure is completed. Suitableguidance elements include: tubes, towers, blades, arms, extended tabs,wires, string, etc. As used herein, extended blades refers to separateelements that attach to the screw head or tabs on the screw head,whereas extended tabs refers to elements that are integrally connectedwith tabs on the screw head or even the screw itself. The extended tabsor extended blades run from a site adjacent the screw head up throughthe incision site. They can be curved (along one or more axis) or bent(along one or more axis) to accommodate the cap and other components.The guidance elements may also be curved or bent in order to be offsetfrom adjacent elements such that they do not interfere if and when theycross. The curvature may be a permanent rounded shape or they may beflexibly curveable or comprised of foldable panels (see FIG. 3A). Thecurves and bends may be permanent and pre-formed or adjustable in situ.The extended guidance elements may also be tapered, threaded and/ornotched to assist in stabilizing the cap or other components as they arelowered down to the screw head.

In some embodiments, the guidance elements comprise two or more bladesthat may be offset from each other so that they do not interfere if andwhen they cross. They can be offset in any functional manner, and canassume different positions around the screw heads (e.g., for staggeredcrossing), bending at different positions (e.g., straight to bent),curvatures that are non-intersecting with adjacent elements (blades fromadjacent screw head), etc.

The extended tabs/blades or other guidance elements on adjacent screwsmay be offset such that they do not interfere with one another when theyintersect. Rather, as they cross one another, the extended tabs/blades(or other guidance elements) smoothly pass by one another. Therefore theextended tabs/blades on adjacent screws can be inserted through the samesmall incision and manipulated within that incision. This may beachieved by tabs/blades, or other guidance elements, on the inside ofone screw and the outside of the other screw. Or, in another manner thetabs/blades for adjacent screws can simply be staggered or misaligned.Another option is for one screw to have a single tab/blade on the medialside while another screw has a single tab/blade on the lateral side.Still another option is for one screw to have extended tabs, while oneor more other screws have flexible wire or wires as guidance elements.

In some embodiments, some of the extended guidance elements (tabs,blades, etc.) on some screw heads may be straight while those on othersare bendable or angled, such that the bendable or angled elements crossover the straight ones to exit the body through the same skin levelincision. In other embodiments, a first screw is connected to a firstextended guidance element in the form of a plurality of blades and asecond screw is connected to a second extended guidance element in theform of a plurality of blades. The plurality of blades of the firstextended guidance element can overlap and/or intersect with theplurality of blades of the second extended guidance element.Advantageously the first extended guidance element and the secondextended guidance element can intersect or overlap at or near a skinlevel incision. By intersecting or overlapping at or near a skin levelincision, this allows both of the guidance elements to extend through asingle, small incision.

The extended tabs/blades or other guidance elements are configured toeasily detach from the screw head upon completion of directing rods,caps, instruments, and other components precisely to the screw head.This detachment process may occur by any number of means, includingbreak-off along a pre-perforated or notched line, burning or melting atthe base of the tabs/blades with an instrument, releasing a mechanicalclamp, etc. The extended guidance elements (e.g.. extended tabs,extended blades, etc.) for adjacent screws may all be attached to theirrespective screw heads at different positions along the screw head toproduce the offset configuration. Or, they may all be attached to theirrespective screw heads at the same location and bent at different anglesto form different configurations that are offset with respect to oneanother when crossed. That is, the extended guidance elements may bebent to come out of the screw head at different lateral displacementssuch that they do not interfere with one another. For a two levelfusion, three offset extended guidance elements (tabs, blades, etc.)attached to three adjacent screws is appropriate. For a three levelfusion, there would be four offset extended guidance elements attachedto four adjacent screws. A four level fusion with five offset extendedguidance elements attached to five adjacent screws, potentially allcoming through the same skin level incision and crossing at some pointat or near the same level skin incision, may also be possible in somesituations.

According to one embodiment the extended tabs/blades/arms and wires canwork together in a “hybrid” concept. The first tab attached to the screwhead is easily detachable. Additional tabs between the screw head anddistal wires protruding from the skin can be added and removed as neededto lengthen or shorten the distance of the guidance trajectory. Oneembodiment has a multitude of breakoff tabs attached to one another inseries, creating a long extended blade. The blade can then be tailoredto the appropriate length, such as at the level of the skin incision, bybreaking the tabs off at the closest breakoff point to that point. Insome embodiments, one or more of the breakoff tabs can be attached to aproximal wire to keep track of and locate the tab within the patient. Asused herein, distal is defined as a space farther from a particularlocation, and proximal is defined as a space closer to the particularlocation. In some embodiments, a portion of a tab or blade that extendsout beyond an incision can be considered a proximal portion, while aportion of a tab or blade that is beneath the incision can be considereda distal portion.

The flexible guidance wires can be used to direct the add-on tabelements during insertion and removal. The guidance wires can serve as aguide to direct add-on tab elements into place within the patient.Alternatively, the guidance wires can be attached to an assembly of oneor more telescoping members (as discussed below) and can be used toadjust the height of the assembly. In other embodiments, a plurality offlexible guidance wires can serve alone as guidance elements to guiderods, tools or locking assembly components to a desired location at ornear the spine. In yet other embodiments, the flexible guidance wirescan be part of a “hybrid” concept and can work in conjunction withtabs/blades/arms to guide elements to a desired location. The rods,tools or locking assembly components can be delivered via the guidanceelements by hand, or in some embodiments, using a stereotactic guidancemechanism and/or by a robot. In fact, the minimally invasive system ofembodiments of the present invention is ideally suited to work withrobotic surgery and stereotactically guided surgery where thetrajectories of spine fixation screws and the screws themselves are alldirected and performed through robotic and stereotactic assistance.

In some embodiments, the upwardly directed guidance elements or portionsthereof may be telescopic such that one element may be pulled out of orpassed over another element. Advantageously, this telescopingcharacteristic can be used to accommodate a greater number of guidanceelements or portions thereof through a single incision. Telescopingtubes are also helpful for guiding a rod through the center of the tubesand thereby inserting the rod through the same common single incision asthe guidance elements.

In one hybrid embodiment, there is a short blade extending upwardly fromone side of the screw head and a longer blade extendingly upwardly fromthe other side of the screw head. The next level has the short blade andthe longer blade each on the opposite side (see FIGS. 36A-36C). Inanother embodiment, short tubes may extend from the screw head, withupwardly extending blades that telescope to adjust the height of theguidance element (see FIG. 39).

In another embodiment, instead of telescoping guiding elements, some ofthe guidance elements or portions thereof may be removable in order tomake room for other elements. After all the elements have been insertedthe top portions of the elements may be placed into their finalpositions. Multiple elements or portions thereof may be inserted througha single incision separately or one piece at a time in order to preventovercrowding near skin level.

In embodiments in which a wire or string that passes beyond the incisionat the skin level is attached to another guidance element, such as anextended tab, the wire or string serves the purpose of making sure thatthe extended tab does not get lost in the wound after it is detached orbroken off. In this manner, wire or string can advantageously be used topull an extended tab or other guidance element out of the wound.

In some embodiments, hinges may exist at the base or along the body ofan extended guidance element, proximal or distal to the point at whichthe guidance element attaches to the screw head. Hinges would permit theguidance element to open up, as necessary, to receive the rod, aninstrument, or another component. The hinges may be on either side ofthe point at which the extended guidance elements join the screw head:the proximal screw head side or the distal extended guidance elementside. If the hinges are on the proximal screw head side they will remainafter the extended guidance elements are detached. If the hinges are onthe distal extended guidance element side they will be removed with theguidance elements. In situations where the guidance elements attach tothe screw head through a mechanical mechanism the hinge might beintegrated into the mechanical mechanism such that detaching theextended guidance elements after they have performed their roledisassembles the hinge.

FIG. 1 shows an embodiment in which the guidance elements 114 areextended blades or extended tabs that connect with the screw head 102anywhere along it from the inside perimeter/inside wall 115 to theoutside perimeter/outside wall 116. In some embodiments, the extendedblades/tabs 114 can advantageously provide more stability than wires andmore flexibility than towers that encompass the rods or other guidedelements. Furthermore, extended blades/tabs 114 and 116 can be attachedto extensions on the screw head or be bent outwards so that theblades/tabs are positioned beyond the edge of the screw head. In thisembodiment, an entire second screw with accompanying screw head andguidance elements can fit completely within the widened space betweenthe blades/tabs that are displaced outside the edges of the screw headon the first screw, without bending or widening the proximal ends of theblades/tabs.

As illustrated in FIG. 1, a system for delivering a rod through anincision to a desired location in a patient can include a first screwhaving a screw head 102 with a pair of extended blades or tabs connectedto an inside wall perimeter 115 of the screw head 102, and a secondscrew having a screw head 102 with a pair of extended blades or tabsconnected to an outside wall perimeter 116 of the screw head 102.Advantageously, each of the pair of blades form a different sizedpassageway or channel through which an implant (e.g, a rod member) orguide tool can be delivered, with the pair of blades attached to thefirst screw head creating a narrower passageway than the pair of bladesattached to the second screw head. Moreover, the system is configuredsuch that the blades or tabs in an inside wall perimeter 115 attached tothe first screw can advantageously criss-cross or intersect with theblades or tabs on the outside wall perimeter 116 of the second screw (asshown in FIG. 2A). The criss-crossing of the pair of blades of the firstscrew and the pair of blades of the second screw can occur at a singleincision of small size, or near the single incision of small size.

In some embodiments, the system is configured such that when the pair ofblades attached to an inner wall perimeter 115 of the first screw headare criss-crossed at or near a single small incision with the pair ofblades attached to an outside wall perimeter 116 of the second screwhead, an implant such as a rod member can be guided down the narrowerpassageway created by the pair of blades connected to the first screwhead. The rod member can be guided such that one end of the rod isseated in a seat of the first screw head. The other end of the rodmember can pass through the passageway created by the pair of bladesconnected to the second screw head and can be seated in the seat ofsecond screw head. While other conventional systems allow for rodplacement across two screw heads, the present system usingcriss-crossing blades at or near a small incision allows for a smaller,less minimally invasive incision in order to achieve the desired result.The criss-crossing blades thus reduce the amount of trauma to thepatient and reduce the amount of time required for healing.

FIGS. 2A and 2B show how the extended blades/tabs 114 are offset 115/116such that in operation upon intersection (shown in both FIG. 2A from theside and in FIG. 2B head-on) they smoothly pass one another withoutinterference. As such, adjacent extended blades/tabs 114 can passthrough the same skin level incision and be manipulated easily through arange of geometries for final positioning. Further, the same devices canbe used generally on all patients with different anatomical dimensions.

FIGS. 3A and 3B show another embodiment in which the extendedblades/tabs comprise foldable panels 117 having creases 118 or hingessuch that they can be configured to curve slightly to wrap or partiallywrap around a guided element (FIG. 3B). Although three panels (twocreases) are shown, more or less panels and creases can be provided.Additionally, although the panels 117 are shown on the inside of thescrew head 102, they could also be positioned along the outside 116 ofthe screw head 102, as shown generally for the guidance elements 114 inFIGS. 1 and 2B. The advantage of the extended blades/tabs with foldablepanels 117 is that they can more easily accommodate guided implants andtools of various shapes and sizes. Essentially a blade or tab can befolded to become a tube or partial tube. Thus the foldable panels haveadvantages of both blades and tubes.

An embodiment of the present inventive system and method is to use oneguidance element 103 on each side of a screw head 102 (as shown in FIG.11A) such that there are two guidance elements 103 per screw shaft 101to securely trap a rod 104 over the screw shaft 101 within the screwhead 102. This embodiment is believed to provide a very high degree ofrod 104 stability, while maintaining a very low volume of stabilizingelements (thereby enabling a very small incision without stressing it).The guidance elements 103 can be part of the screw head as an extensionof the screw head itself. Or, the guidance elements 103 can beindependent elements attached to the screw head 102 through (i) theguidance element itself, (ii) an extension of the guidance element thatis formed of a material that is the same as a material from which theguidance element itself is derived, (iii) a thread material thinner thanthe guidance element, (iv) a short tower, or (v) an intermediate elementincluding an extensor/extended tab 112, flexible sheet, flange 110, ormechanical device / clamp 113 as discussed further herein, among otherpossibilities. A single guidance element 103 may be attached to a screwhead 102 at a single location or in two or more locations 111 asillustrated in FIG. 11B. If the screw head has edges or corners,guidance elements attached to those corners will eliminate thepossibility that a rod or locking mechanism is caught on the edge orcorner during insertion of the same.

In some embodiments, as a substitute for the extended blades/tabsguiding elements, a plurality of wires can be joined to form a “wall”guiding element similar to the blades/tabs. In some embodiments, theplurality of wires can be flexible, and can be joined by a cuff or strap(e.g., a metal strap) to form a guiding element simulating a long“blade” or “tab” for guiding an implant or tool to a desired location ina patient. The use of a plurality of wires in the form of a “wall” canprovide increased flexibility relative to conventional systems, therebyallowing for “wall” guiding elements to criss-cross at various angles ator near a single incision. The “wall” of guiding elements can similarlybe configured in a circular shape to form a tube by a circular shapedstrap that is attached to one or a few of the wires, thereby allowingthe wires to bend independently of each other. A “wall” of wires orguiding elements need not be densely packed. The distance between wiresor guiding elements need only to be smaller than the size of the rod orlocking assembly such as a locking nut. This way, the rod or locking nutcannot “escape” out of the “wall” formed by the wires/guiding elements.

FIG. 4 shows another embodiment for a screw cap placement mechanism, ascompared to a simple cap 106 as shown in FIGS. 20A and 22A. In thisembodiment, the screw cap portion comparable to 106 (in FIGS. 20A and22A) is 119. The screw cap portion 119 can be delivered to retain a rodimplant (such as rod 104 in FIG. 20A) in the seat of a screw. The screwcap portion 119 can stay on permanently or can be removable to retainthe rod. The remaining portion 120 is a screw cap guidance element to beused with extended blades rather than guiding the cap directly downguidance wires (as in FIGS. 20A and 22A). The screw cap guidance element120 has a threaded hole 122 with which the screw cap engages and aprotruding portion 121. The protruding portion or extensor element 121engages with a corresponding cutout 123 in the extended guidance element(blade, tab, arm) 114 as shown in FIG. 5.

The entire screw cap guidance element 120 can be used to hold thethreaded screw cap locking assembly 119 and lead it downward to thescrew head 102 using the upwardly directed extended guidance element 114as a support rail and directional guide. As shown in FIGS. 6A and 6B,the screw cap portion 119 can be guided downward using the extendedguidance element 114. When the combination unit (120 and 119) reachesthe screw head 102, the screw cap 119 inside can be screwed downward outof the cap guidance element 120 into the screw head 102 immediatelyabove the screw within the screw seat. The cap guidance element 120 canthen be removed with the extended guidance element 114, for example bysimply detaching from the screw head 102 as shown in FIG. 6C.

FIGS. 7A and 7B illustrate how the screw cap guidance elements 120 workas part of the offset guidance system. In this system, extended guidanceelements (blades/arms) 114 for adjacent screws can intersect one anotherwithout negative interference. With the extended guidance elements 114crossed, screw caps 119 can still be led down to each screw head 102simultaneously by the respective screw cap guidance elements 120 withoutnegative interference. Note how the screw cap guidance element 120 forone screw cap 119 (upper) has its protruding portion 121 engaged with aslot 123 in the left extended guidance element 114 of a first screw head102, while the other screw cap guidance element 120 for the other screwcap 119 (lower) has its protruding portion 121 engaged with a slot 123in the right extended guidance element 114 of a second screw head 102.Additionally, FIG. 7B shows one option for the attachment of theextended guidance elements 114 to the screw head 102 in which bothextended guidance elements (blades/arms) 114 for the lower screw attachto its outer edges on both the left and right sides (outside/outsideorientation 129). In order for the criss-crossed configuration shown inFIG. 7A and 7B to take place, at least one blade of the first screw ispreferably flexible, bendable, removable, telescoping, etc. in order toallow the second screw to be placed within the same incision. After thesecond screw is placed, the blade of the first screw can be replaced,moved, or telescoped to a position in between the blades of the secondscrew.

FIGS. 8A and 8B show another option for the attachment of the extendedguidance elements 114 to the screw head 102 in which both extendedguidance elements (blades/arms) 114 for the upper screw attach to itsinner edges on both the left and right sides (inside/inside orientation130). Thus, a screw head 102 with extended guidance elements(blades/arms) 114 having an inside/inside orientation 130 can fitcompletely inside another screw head's extended guidance elements 114that have an outside/outside orientation 129 to cross or intersect in anon-interfering, offset manner. In this arrangement the ordering ofblades is: a blade of a first screw; a blade of a second screw; a secondblade of the second screw; and a second blade of the first screw. Inorder for this outer-inner configuration shown in FIGS. 8A and 8B totake place, the screw with the outside/outside orientation is placedfirst. The second screw with the inside/inside orientation is placedbetween and through the outside/outside blades of the first screw. Theoutside/outside blades is preferably flexible, moveable, removable,telescopic, or adjustable in height to allow the second screw to passthrough the same incision.

FIGS. 9A and 9B show further options for the attachment of the extendedguidance elements 114 to the screw head 102 in which both extendedguidance elements (blades/arms) 114 for the upper screw attach to itsright edges on both the left and right sides (inside/outside orientation128). For the lower screw the extended guidance elements (blades/arms)114 attach to its left edges on both the left and right sides(outside/inside orientation 127). Accordingly, the two sets of extendedguidance elements 114 for these adjacent screws can be made to intersectin a non-interfering, offset manner in which the consecutive arrangementis: a blade of a first screw; a blade of a second screw; a second bladeof the first screw; and a second blade of the second screw. In order forthe criss-crossed configuration shown in FIG. 9A and 9B to take place,at least one blade of the first screw is preferably flexible, bendable,removable, telescoping, etc. in order to allow the second screw to beplaced within the same incision. After the second screw is placed, theblade of the first screw can be replaced, moved, or telescoped to aposition in between the blades of the second screw.

FIGS. 10A-10C show another screw cap guidance element called aconcentric screw cap placer. The concentric screw cap placer 125 hasinner threads that engage with the screw cap 119 along with outerthreads 126 that engage with threads on the inside of the extendedguidance elements (blades/arms) 114 (not shown). The concentric screwcap placer 125 allows the screw cap 119 to be placed down extendedguidance elements with blades that are wider apart than the diameter ofthe screw cap 119. The threaded feature of the concentric screw capplacer allows a rod to be reduced downwards towards the seat of thescrew head by the cap placer even when the guidance elements are widelyspaced such as in an outside/outside orientation, as shown in FIG. 8B.The extended guidance elements (blade/arms) 114 should have threads atleast at the bottom near the screw head 102 to guide this type of screwcap placer more accurately close to the screw head. After placing thescrew cap 119 on the screw head 102 above a rod 104 in the seat of thescrew head 102, the concentric screw cap placer 125 may be unscrewed outof the body, upward and off of the extended guidance elements 114. Orthe extended guidance elements 114 could be detached and the cap placer125 removed with them. Or, for extra security or support, in somesituations the concentric screw cap placer 125 may be left in positionabove the rod 104 and screw cap 119, even after the extended guidanceelements 114 are unscrewed from it and detached.

In alternative embodiments, a system can be provided that does not use ascrew cap 119, set screw and screw placer 125, or guidance element 120.For example, as shown in FIGS. 30A-30D, another embodiment for the rodlocking assembly is illustrated in which a screw cap 119 or set screwand screw placer 125 or guidance element 120 (collectively as in FIG. 4thru FIG. 10C) are not necessary. Rather, the locking assembly 124 shownhere is part of the screw head 102 itself. Integrating the lockingassembly 124 with the screw head 102 simplifies a surgical procedure byeliminating the step of guiding a separate locking assembly (e.g., 106as in FIG. 20A, or 119/120/121 as in FIGS. 4 through 9B, or 119/125/126as in FIGS. 10A-10C) down to the screw head 102. Instead, after the rod104 is placed, the screw head 102 itself (or portions of it 124) cansimply by manipulated to lock the rod 104 in position. For example, thescrew head 102 might be turned or rotated such that extensions 124 fromit trap the rod 104 against its base 102. Alternatively, portions of thescrew head 102 can be manipulated to snap into place around or over therod 104 or to converge inward to tighten the hold on the rod 104.

FIGS. 11A-11C show embodiments of a minimally invasive system comprisinga screw head having guiding elements in the form of wires to assist inthe delivery of a rod to the seat of the screw head. The guidingelements create a pathway or channel for the delivery of the rod.Advantageously, the one or more guiding elements on one screw head canintersect with the one or more guiding elements on a second screw head,for example at, near, above or below a skin incision, and cansimultaneously assist in blocking tissue or muscle from the pathwaywhich could block the path of the rod during delivery

In FIG. 11A, a single guidance element 103 illustrated in the form of asingle wire is attached to the screw head 102 having a first wireportion extending from one side of the screw head and a second wireportion extending from the other side of the screw head. The two wireportions in one embodiment may be separate wires. Alternatively, FIGS.11B and 11C illustrate a second configuration in which one or moreshorter guidance elements or wires 111 are attached to the screw head102 and also attached to a single or multiple elongated guidanceelements or wires 103 at their other end. Multiple short guidanceelement 111 attached directly to the screw head 102 may provide greaterstability for an easier alignment. To accommodate this multiple guidanceelement configuration 111, insertion instruments having side loops (notshown) through which the guidance element passes also have side loops toaccommodate the larger area created by the fanning out configuration ofthe multiple short guidance elements 111 close to the screw head 102.Thus, the side loop attached near the tip of the insertion tool will beas wide as the screw head to accommodate all the short guidance elementsat the screw head. Above the transition zone (from multiple guidanceelements 111 to a single guidance element 103) the insertion tool willhave smaller side loops that only allow a single guidance element topass.

In another embodiment there may be a single guidance element or wire 103on only one side of each screw 101/102 or screw head 102. Thisembodiment further reduces the volume of stabilizing elements (screwhead guidance elements) that must fit through the minimal incision butmay reduce rod stability. When only one screw head guidance element 103is used per pedicle screw 101/102 it is recommended that at least onerod retention thread 105 also be used (see FIGS. 17 and 18 forillustration of the rod retention threads 105). FIGS. 19A-19F illustratethe steps for delivering the rod to the screw head 102, with the rodretention threads slid over the guidance element or wires 103. FIGS.20A-20C illustrate a screw cap 106 being delivered between the wires 103to the screw head 102, where it may be screwed into the screw head 102.The screw head guidance element 103 should be inserted through the loopformed by the rod retention thread 105 along the lateral side of the rodbody 104. Rod retention threads 105 can be useful when the rod 104 isbent and the orientation of the bend has to be maintained in a properdirection to match the configuration of the screws. Sometimes a bent rodrotates when inserted and may not fit into the screw heads because thebend is rotated incorrectly so as not to match up with the orientationof the screw heads. Retention threads can reduce this risk and allow forcorrection in situ if the upwardly directed extended guidance element isin place properly through the thread. Retention threads are also usefulto align a rod to fit into the screw heads when the rod does not have aspherical cross section. For example, the rod can have an oval in crosssection so that it is stronger in flexion extension (the longer axis ofthe oval cross section) than in lateral bending (the shorter axis of theoval cross section). Retention threads can limit rotation and force therod to sit down into the screw heads. When retention threads are used,it may be useful to eliminate the outer edges and corners of the screwhead as seen in FIG. 11C. Additional short wires connecting the singleupward projecting guidance element to the outer corners would allow theretention thread to slide over the outer edges of the screw head.Alternatively, the outer edges of the screw head is tapered to allow theretention thread to slide down the outer aspect of the screw head whenthe rod is placed down into the screw head.

In some embodiments, to assist the rod 104 in staying within the guidingelement 103 (or any other guiding elements discussed herein), a rod wire(not shown) can be provided that protrudes out of a leading end,trailing end or both of the rod. The rod wire in some embodiments may becapable of snapping off. The rod wire may also be hinged or bent upwardrelative to the rod to ensure that the rod is delivered in the correctmanner. In some embodiments, the hinge may comprise a screw mechanismwhere the rod wire is screwed onto the rod. Other attachment mechanismssuch as described for the guidance elements may also be utilized. Theuse of the rod wire can provide guidance as to the orientation of therod as it moves downwardly through the guidance elements, as well as ofthe position of the rod relative to the guidance elements. This way, itis possible to place the rod in a desired orientation (e.g., vertically)as it moves downwardly through the incision and the guidance elements.

In some embodiments, the rod can be oriented vertically until it reachesa first screw, and afterwards, can be rotated down into the second screwhead. In other embodiments, the leading end of the rod is held andguided by a tool that is guided and slid down over the guidance elementsof the second screw. In still another embodiment, the leading end of therod is guided by retention threads that only trap the guiding element ofthe second screw while the trailing end of the rod is trapped betweenthe guiding elements of the first screw by the rod wire. Accordingly,the rod wire serves as a detachable flexible extension that keeps thetrailing end of the spinal implant within the first guiding element whenthe leading end is first delivered to the second screw by the secondguiding element. The flexible rod wire can also be loosely and partiallycoiled or wrapped around one of the guiding elements of the first screwafter the rod wire has passed through and between the guiding elementsof the first screw. This configuration also ensures that the trailingend of the rod slides between the guiding elements into the screw headof the first screw. Once the rod is in a desired position, the rod wirecan be snapped off, either manually or when enough tension builds fromchanging the orientation of the rod relative to the wire.

In another embodiment, instead of one or more guidance elements 103,there may be one or more upwardly directed shafts that are not round(not shown) and are attached to a side of the screw head 102. The uniqueshape of the shaft would prevent insertion tools from turning orrotating around the shaft (e.g., during their descent to approach thescrew head 102). Thus any shaft that is not cylindrical would be capableof guiding tools that have a complementary non-cylindrical shaft holderattached to the tool. For example, a shaft that has a cross section ofan oval, square, rectangle, triangle, cross, trapezoid, star, or anyother shape besides a circle would be able to prevent an insertion toolfrom rotating around the shaft as long as the insertion tool is equippedwith a complementary shaped holder through which the shaft fitsprecisely. As long as the screw head 102 is multi-axial, there would besome flexibility in moving the shaft around in the incision.

The screws 101 and screw heads 102 themselves may also have any one ofseveral different vertical and horizontal cross-sections including bothcircular and non-circular, rectangular, square, hexagonal, etc. Thescrews 101 and screw heads 102 are preferably made of a titanium alloyor stainless steel. In some embodiments, the screw heads 102 include aseat in the form of a channel for receiving a rod member. The seat canassume various shapes, such as half spherical or cylindrical.

The rods 104 are preferably cylindrical but in other embodiments theymay have a non-circular cross-section (triangular, square, hexagonal,etc.) so long as the seat of the screw head 102 is shapedcorrespondingly to accommodate. The rods 104 are preferably formed of atitanium alloy but may also be made of any other metal (commerciallypure titanium, stainless steel, etc.) or a biocompatible minimallyflexible polymer such as polyetheretherketone (PEEK). The rods can beuniformly or non-uniformly (same or different degrees of flexion alongdifferent axis) rigid, semi-rigid, semi-flexible, or flexible. The rodscan be straight or angled and may be pre-bent or bendable in situ.Flexible rods may be formed of a uniform flexible substance such as PEEKor may incorporate a joint in the middle of the rod which bends. Or,cuts in a hollow rod allow bending of the rod similar to a spring.

In some cases, other elements, including connectors or T-connectors, canbe also introduced, with or without assistance of the upwardly directedextended guidance elements, to cross the spine horizontally and connecttwo parallel rods to provide additional support.

In another embodiment there may be more than two guidance elements 103per pedicle screw 101/102. Preferably, if more than two guidanceelements per screw are used, there is at least one guidance element oneach side of the screw with more than one guidance element on at leastone side. An equal number of guidance elements on each side improvesstability and prevents lopsidedness. However, every patient's anatomy isslightly different and when curvature (e.g., scoliosis) and/or otheraggravating conditions are present stability during rod 104 insertionmay be best achieved by an asymmetric distribution of screw headguidance elements 103 around the perimeter of a screw head 102. In anycase, the spinal surgeon is in the best position to make this decisionabout the appropriate screw head guidance element 103 and rod retentionthread 105 set-up to use based on the individual needs of a particularpatient.

The guidance elements 103 on any one screw 101/102 can be placed atvarious positions around the periphery of a screw (rather than just onthe sides) for enhanced stability and control. Screw 101/102 is used torefer to the entire screw including the screw shaft 101 and the screwhead 102 collectively. The guidance elements may be uniformlydistributed and symmetrical around the periphery or they may beasymmetrical and staggered. For example, having four guidance elementson a screw head (e.g., one guidance element on each edge: north/top,east/right, south/bottom, west/left) helps provide that the screw head102 is oriented along the axis of the rod 104 during transport of therod through the incision and into a first screw head. Limiting the openregions around the perimeter of a screw head 102 by effectively creatinga guidance element cage can also force the rod 104 to turn in the rightdirection (or force the screw head to turn to accommodate the rod) whenit moves from a vertical longitudinal to a transverse lateralorientation after placement of a first end in a first screw head whilethe other end is being directed for placement in a second screw head.The number of guidance elements, their sizes (e.g., diameters andlengths), shapes, flexibility, and strength may be adjusted to suit aparticular procedure in a particular patient based on the incision sizeto optimize screw stability and facilitate rod alignment while avoidingentanglement of too many guidance elements. Contemplated embodimentsinclude those with from 1 to 10 guidance elements per screw/screw head,and more especially those with 2 to 4 guidance elements.

Instead of multiple long guidance elements connected to the screw head102 on each side, a single long guidance element 103 (or thread) isconnected to several short guidance elements 111 which in turn areconnected to each side of the screw head. Thus, multiple guidanceelements 111 are still connected to each screw head 102 but thesemultiple guidance elements are also connected to one another in an areaabove the screw head to form single guidance element 103 extendingthrough the incision. These multiple short guidance elements 111 maystill function to bound or limit the movement of a rod 104 at least atthe base of the screw head 102. The short guidance elements 111 give theadvantage of creating a guidance element cage by which the rod 104 isforced to sit down into the seat of the screw head 102. The long singleguidance element (or thread) 103 reduces clutter and confusion at theskin incision that occurs when too many guidance elements are present.The multitude of short guidance elements 111 distributed away from thelongitudinal entry axis into approximately the same axis along which therod 104 will ultimately lay also allows the long guidance element 103and accompanying instruments to adjust the orientation and angle of thescrew head 102 in this axis (the rod axis, approximately perpendicularto the longitudinal entry axis used during rod insertion). The screwhead 102 is configured to form a concave channel in which the rod 104will eventually come to sit/rest. The concave channel may be U-shapedwhen a vertical cross-section is taken but any substantially concaveshape suited to retain a rod 104 and with dimensions corresponding tothose of the rod 104 will work. The upper edges of the screw head 102itself or those of another intermediate element 110/112/113 to which itis attached, are configured to receive an incoming rod at a wide rangeof angles and smoothly direct it into the proper angular configurationto fit into the screw seat.

As an alternative to the screws 101 or the screw heads 102 beingattached directly to upwardly directed guidance elements 103 or guideshafts, there may be an intermediary flange, flanged leaflet, sheet 110,extensor/extended tab 112, a mechanical clamp/device 113, or otherelement in between the two. The screw 101/102 or screw head 102 at itsouter edges may transform into (integral therewith) or attach to aseparate element that is directly attached to the guidance element/shaft103 such that the screw 101/102 or screw head 102 and the guidanceelement 103 are indirectly connected. The intermediate element ispreferably specially adapted to readily detach from the screw 101/102 orscrew head 102 when desirable, such as after securing the rod 104 inproper position and locking it in place. Detachment may be through asnap-off/pop-off mechanical mechanism that might be activated through apush-button on a surgeon's tool; through tearing along a perforation;through cutting, twisting, wagging, burning, heating, radiating,ultrasonically vibrating, electrifying/electrocuting, dissolving,unscrewing, or any other means. In this case with the guidance elementsor upward shafts 103 attached directly to the intermediate and readilydetachable element 110/112/113 the guidance elements 103 themselves maybe more securely fastened to the intermediate element 110/112/113. Forexample, the guidance elements 103 might be soldered or welded to anextensor tab 112 that snaps into/onto and snaps out of/off of a grooveor protrusion on the screw head 102. At least a portion of the extensortab 112 may be threaded to mate with a screw 101/102 or screw shaft 101having corresponding threads or to align a rod 104 having somecorresponding threads.

The intermediate element may be in the form of a sheet 110 of a verythin material that is both flexible and can be tensed by pulling ortightening. When pulled tight the sheet 110 functions to guide the rod104 into the seat of the screw head 102. Such material may be rubber.

An intermediate element may be an inwardly tapered flange 110 attachedto an inner top edge of the screw head 102 and placed symmetricallyabout the screw seat in which the rod 104 sits. Such a flange 110 isconfigured to allow a malaligned rod 104 or screw head 102 to rotate andadjust relative to one another as the rod is inserted into the seat ofthe screw head until the two are acceptably aligned. The inwardlytapered sides of the flange 110 may take the form of convexly curvedwings 110 that form a channel for the rod 104 between them. FIGS.26A-27B show embodiments of flanged attachments 110 that help the rod104 to find the proper orientation to best fit into the screw head 102.As shown, each attachment 110 is preferably convex in a directiontowards the rod so that as the rod approaches the screw head, theentrance to the screw head can accept a large range of angles in whichthe rod is oriented and still receive the rod, gradually improving therod's orientation as it gets closer to the seat of the screw head. FIGS.27A and 27B show two sequences of lowering a rod into a malaligned screwhead (or, of lowering a malaligned rod into a properly aligned screwhead) using flanged attachments. The bi-convex nature of the flangedattachments permits the rod to twist and adjust as it is lowered.Otherwise, without the flanged attachments, in a malaligned situationthe rod would hit the edges of the screw head and would not be able tobe lowered further. The flanged attachments are shown here as detachableelements on the screw head; however, another preferred embodiment is aflanged and convex shaped rod guide built into the tops of opposingsides of the “U” shaped screw head (e.g., may be integrally part of thescrew head interior itself). The flanged attachments 110 in oneembodiment may further have wires (not shown) extending upwardlytherefrom as described elsewhere herein.

Or, the intermediate element may be an extensor tab 112 with straightrather than convex sides. Preferably, the tab is triangular which may beformed by removing the corners of an otherwise rectangular tab. Thewider base of the triangle may attach to the screw head 102 as shown inFIGS. 28A-28C.

The screw head 102 or intermediate element 110/112/113 provides achannel into which a rod 104 can be easily guided by the upwardlydirected guidance element 103 or guide shaft. The screw head orintermediate element is advantageously adapted to accept a large degreeof malalignment of the rod and the screw seat relative to one anotherand then guide the rod into the screw seat until substantially perfectalignment is achieved. The advantage of this is that the system does notrequire starting over, pulling out, and reinserting the rod when itturns out the initial positioning is not ideal.

The guidance elements, threads, and intermediate elements describedherein may be attached to the screw or screw head on the outside, on theinside, or through a cannulated portion of the downwardly directed screwshaft 101. Many attachment locations are possible so long as it does notinterfere with the ability of the screw shaft 101 to be drilled into thepedicle and the ability of the rod 104 and locking assembly 106 to bereceived into the seat of the screw head 102.

The guidance element, thread, or upwardly directed shaft 103 may beattached to the downwardly directed screw shaft 101, the screw head 102,or an intermediate element (e.g., flange, sheet 110, extensor/extendedtab 112) with glue, soldering, thread, sutures, string, a mechanicalclamp 113, etc.

In embodiments in which a mechanical clamp 113 is used to connect theupwardly directed extended guidance element 103 to the screw head 102,the clamp 113 preferably has two leaves that are connected under thehead 102 or at least below where the rod 104 comes down so as not toimpede the path of the rod. After closing the locking assemblies 106 tosecure the rod 104 in place within the screw head 102, the clamps 113can be removed. Removing the clamps 113 from the screw head 102 alsoremoves the guidance elements 103 attached to the clamps 113. The clamps113 may be removed by any means feasible in the limited space including(but not limited to): (i) by breaking the connection (like detaching theextended tabs 112), (ii) by cutting a material that holds the 2 leavestogether, (iii) unclamping or unbuckling, and (iv) unvelcro-ing.

Or, in some embodiments the locking assembly may be part of the clamp113 such that the clamp is not removed but remains to hold the rod 104(see FIG. 29A). In such situations, the guidance elements 103 are simplydetached from the clamp-locking assembly combination unit.

Instead of a mechanical clamp with moving parts, the intermediateelement (between screw head 102 and guidance elements 103) may alsosimply be a metal or plastic device that has no moving parts but trapsthe head 102 securely into it. The intermediate metal or plastic devicecan be removed by means including (i) snapping a thin center partconnecting 2 halves of the device, or (ii) cutting a string thatconnects two parts of the device. If the locking assembly 106 for therod 104 is distinct from the intermediate metal or plastic device, thenthe device can be removed along with the guidance elements after the rodis placed. If the locking assembly is integrated with or dependent uponthe intermediate metal/plastic device, then the device should stay inplace after the guidance elements 103/111 only are detached from it.

In another embodiment illustrated in FIGS. 21A-21F, the guidance element103 or an extension thread 107 thereon can be attached to the areawithin the screw head 102 where the rod 104 would eventually sit, suchas at the base or sides of the screw head and/or to the upper end of thedownwardly directed screw shaft 101. For example, the guidance element103 or its extension 107 may be attached within the cannulated portionof a cannulated screw. By using a flexible guidance element or extensionthread 107, the guidance element/thread can wrap around the rod 104 asthe rod is seated into the screw head 102. The guidance element/threadcan then be threaded through cannulated tools and a cannulated lockingassembly 106 above the rod. FIGS. 22A-22C show how threads 107 can bewrapped around the rod and brought together to guide a cannulatedlocking assembly (e.g., cap 106) as well as other cannulated tools (notshown) down to the screw head 102.

Optionally, color-coded guidance elements 103 and/or screws 101 may beprovided to assist doctors, technicians, and medical personnel inidentifying elements, performing the procedure, and monitoring progressduring follow-up visits. Or, some other form of visual coding, such aswith particular materials and/or only visible under certain conditionsmay be used to distinguish guidance elements, screws, and other elements(e.g., fluorescent markers, radioactive isotopes, radioopaque markersvisible on X-rays, magnetic nanoparticles, etc.). Another alternative orcomplementary coding means can be sensed by touch (different surfacetextures) or sound (tactile or auditory) rather than or in addition tovisually. The coding could be correlated with right and left sides ofthe body, medial vs. lateral elements, guidance element/screw sizes,guidance element/screw shapes, guidance element flexibility, and/orguidance element strengths, among other possibilities. This list ofvariables with which a coding or tagging system may correspond isintended to be illustrative rather than exhaustive. One coding systemprovides markers or color coding for guidance elements that are intendedfor the medial side of the rod versus those intended for the lateralside of the rod. This coding would allow for easy separation of theguidance elements 103 when the rod 104 is inserted. This coding wouldalso help the insertion of tools and the locking assembly 106 along themedial side and lateral side guidance elements 103. Some elements(guidance elements 103, screws 101, screw heads 102, rods 104, retentionthreads 105, locking assemblies 106, etc.) with similar characteristicsmay be coded in groups such as all medial side guidance elements beingred while all lateral side guidance elements are green. Another variablefeature that can be used to code medial and lateral guidance elements islength of the guidance element. Shorter lengths can code for medialwhile longer lengths code for lateral or vice versa.

Any locking assembly 106 can be used in certain embodiments of thepresent invention. The precise design of the locking assembly 106 is notimportant so long as it is configured to retain the rod 104 within thescrew head 102 for a secure and lasting stabilization. Examples oflocking assemblies 106 that might be employed include screw-on nuts,press-on caps, fast-drying glue, a tiny swinging gate or door with alatch, a series of elements that can be deployed to tighten around theperiphery of the rod, etc.

Since a rod connects two or more separate vertebrae, the rod can firstbe secured into position (locked or tightened) though the lockingassembly on a first vertebra and then subsequently on a second vertebra.In some cases after the rod is firmly secured to the screw on the firstvertebra, the relative positioning of the vertebrae can be adjusted bythe surgeon by moving the vertebrae closer together or farther apartbefore the rod is secured to the screw on the second vertebra. With onlyone side of the rod locked into place the other side of the rod caneasily be adjusted in position. For example, the rod can verticallyslide forward or backward through the locking assembly until the desireddistance spanned by the rod between locking assemblies is obtained.

The guidance elements 103 can be attached to the screw heads 102 by anumber of mechanisms. The retention threads 105 can be attached to theends of the rods 104 by the same assortment of mechanisms. The simplestattachment mechanism is to solder or glue the guidance element/thread tothe screw head/rod. The solder or glue can then be cut or broken offlater. Neither the lateral retention threads 105 on the rod 104 nor theupwardly directed extended guidance elements 103 on the screw 101/102,or on the screw head 102, are needed after the rod 104 has been securelyplaced within the screw head 102.

The retention threads 105 on the rod 104 that hold it close to theguidance elements 103 as it is guided into position are preferably madeof a flexible material including metal, nitinol, rubber, suture,plastic, polymer, and biodegradable material. The retention thread 105should be easily removable after the rod 104 has been secured in analigned position in the seat of the screw head 102 and locked in.

Or, the guidance element/thread could be threaded into a threadedconnector in the side of the screw head/rod so that the guidanceelement/thread is unscrewed at the end of the case.

Other embodiments include attaching the guidance element 103/retentionthread 105 by dissolvable sutures attached or tied to the screw head102/rod 104 and to the end of the guidance element/retention thread witha small loop or grooves in the screw head/rod. Suitable dissolvablesuture materials include biocompatible synthetic absorbable materialssuch as those made primarily of polyglycolic acid (PGA) or other provencompositions. Specific brands of materials include Vicryl™ (fromEthicon), Biovek™ (from Dynek), Visorb™ (from CP Medical), Polysorb™(from Covidien's Syneture), and Dexon™ (also from Covidien's Syneture).The materials can be tailored to degrade or absorb in an amount of timethat corresponds with sufficient internal healing to successfully holdthe fusion. For example, standard Vicryl™ typically maintains tensilestrength for three to four weeks. The materials may also be impregnatedwith drugs or biomolecules (e.g., triclosan) to accelerate the healingprocess and prevent infection. When the biodegradation (e.g.,bioabsorption, bioerosion, etc.) time for the suture material is toolong and the sutures are unnecessary immediately following the procedurethe sutures can instead be promptly cut or burned at the end todisconnect the guidance element/retention thread from the screwhead/rod.

Yet another option for the “guidance element to screw head” or“retention thread to rod” attachment mechanism is to secure using amaterial that burns, breaks, or dissolves upon the application ofcurrent (e.g., radiofrequency current). This option permits theconnection to be easily broken by simply passing current through theguidance element or thread. Preferably, the guidance element/retentionthread breaks down in response to current applied outside the skin. Or,an insulated guidance element can be used to apply current internally ina targeted and minimally invasive manner. An insulated guidance elementwould allow the current to pass directly from an external tip (outsidethe body) to the current-sensitive material at an interior tip near thepedicle screw.

In still another embodiment for attachment, the selected material (e.g.,elastic string or rubber) is both flexible and can be tensed by pullingor tightening. The key is to use very thin material that can be bothflexible and become tense. These dual properties allow the material toreliably guide the rod and tools down through the small incision withoutbreaking while adapting to share the limited space. Unless it is alsobiodegradable the flexible, tensile material of string/rubber will needto be cut/broken/burned off or untied from the screw head and guidanceelement (or rod and retention thread) at the end of the procedure.

Instead of using an intermediary material to connect the guidanceelement to the screw head and/or to connect the retention thread to therod, another possibility is for the guidance element and/or retentionthread to be formed of the same materials as the intermediary connectorsdescribed above. In this situation, it is the guidance element orretention thread that is itself burned or cut at the end of theprocedure.

The final result in all cases is a clean, successful pedicle screwfusion just like that which results from screws and rods used in an openprocedure but with a smaller incision and fewer components.

The material through which the rod-guiding guidance element is attachedto the screw head may be the same material of which the guidance elementitself is derived or a separate material. The guidance elementsthemselves are preferably formed of a biocompatible metal having bothstrength and durability. In a preferred embodiment, the guidanceelements are formed of nitinol (nickel titanium alloy).

The material through which the retention threads 105 of the rod 104 areattached to the ends of the rod may be the same material of which theretention threads themselves are derived or a separate material. Theretention threads are preferably formed of a biocompatible metal havingboth strength and durability. In a preferred embodiment, the retentionthreads are formed of nitinol (nickel titanium alloy). In anotherembodiment the retention threads of the rod to be made from abiodegradable thread so that it does not have to be removed afterplacement. Another advantage of thread is that it would not interferewith the rod and cap locking mechanism 106 if it were caught in betweenthe cap 106 and screw head 102 threads.

To complement the guidance element guides 103, certain embodiments ofthe present invention also provide a special rod 104, with its ownretention threads 105, that can fit between the guidance elements. Byattaching a small loop or ring at the ends of the rod, two threads canbe tied though the loops with good tension along the sides of the rod.This way the guidance elements 103 will pass in between the rod 104 andthe thread 105 to prevent the rod from slipping out and around the mostsuperior or inferior guidance elements. (See FIGS. 17 and 18.) Theretention thread 105 may also be attached to the rod by means other thanloops or rings at its ends. The rod 104 may have holes or piercingstherein for securing the thread to it. The rod may have grooves at itsends with which the thread engages. The thread 105 may be glued on nearthe ends of the rod. Rod retention threads 105 restrain the rod 104 toriding the guidance elements 103 and eliminate the risk of internal roddisplacement away from the target screw site 102. The retention threads105 also expedite rod 104 placement into the screws 102/101 to decreasetotal procedure time.

The retention thread 105 may take the form a strip or long sheet ofmaterial rather than an ordinary thread. The retention thread materialshould be flexible, strong, and biocompatible.

The steps for the placement of the pedicle screws and rods for a“Microfusion” approach are as follows. First, using fluoroscopy orstereotactic guidance, a single small skin incision 1-4 cm lateral to amidline that will accommodate all pedicle screws is localized. Next,using either a percutaneous Jamshedi/Kirschner-guidance element(K-guidance element) approach, a Wiltse muscle splitting approach, ortube system, the pedicle screws are placed (see FIG. 12). The pediclescrew inserter may have loop attachments that hold the side guidanceelements of the pedicle screw during placement. Or, the insertion toolor device that positions the pedicle screw may have protrusions (orslots/grooves) that mate with corresponding slots/grooves (orprotrusions) on the upwardly directed extended guidance elements(similar to how the cap is guided in FIG. 4). Once the pedicle screw isplaced, the insertion tool or device needs to be removed to make roomfor the placement of the other screw(s), the rod, and optionally, aseparate locking assembly.

After each pedicle screw is placed, the side guidance elements arepushed to the side(s) of the incision to make room so that the otherscrews can be placed around or between the guidance elements already inplace. Typically it is preferable to insert additional screws in betweenthe guidance elements of the first screws for cases where pairs ofwires, blades, or tabs are used. After all screws are placed, a screwhead turner is inserted and guided down to the screw heads along eachpair of guidance elements to align the heads of the screws inpreparation for receiving the rods (see aligned screw heads in FIG. 13).

With the screw heads aligned, the side guidance elements are splitbetween the medial and lateral sides. Then a rod is slid in between themedial and lateral guidance elements into the screw heads. Preferably,the rod should be sized and bent before insertion. Markers on theguidance elements at predefined distances from the tip of the guidanceelements can help guide the surgeon in correctly sizing and bending therod. Guidance elements coming out of a single incision are similar tolight rays that have been focused by a convex lens. These light raysconverge at a point and then create a mirror virtual image on the otherside of the focal point. This same concept can be used to create amirror image of the rod to guide the sizing and bending of the rod toaccurately fit into the screw heads. (See FIG. 14). The depth of eachguidance element relative to the intersection point near the skinincision is reflected outwardly on that same guidance element and equaldistance away from the intersection point. By connecting the reflectedpoints on the guidance elements proximal to the intersection point, avirtual image of the curvature and length of the rod is accuratelyestimated. The rod is then lowered through the guidance elements by oneor a combination of mechanisms including retention threads, rod holdersthat are guided by the guidance elements, and rod wires. After each endof the rod is properly positioned within a screw head, locking nuts orcaps are screwed on the screw heads to secure it in place. Or, acompressor that is guided by the guidance elements is used to compresspedicle screws on adjacent levels and then final tightening can be doneduring compression. Other instruments can also guided by the guidanceelements, such as to compress, distract, or move one vertebra relativeto another (e.g., for spondyloisthesis or scoliosis). The guidanceelements are then removed by any means including cutting, twisting,wagging, burning, radiating, dissolving, unscrewing, etc. (see FIG. 15and FIG. 16, left side). Once the screws and rods in all vertebraeto-be-fused along one side of the vertebral column are stabilized, thecontralateral side can be similarly stabilized if indicated (see FIG. 15with one rod, preparing for the second, and FIG. 16 with two rodsplaced).

Embodiments of the present invention can be used to dynamicallystabilize or fuse vertebrae while at the same time removing a defectiveintervertebral disc and inserting a spacer in its place. The spacer mayinclude bone graft material or bone inducing material incorporatedtherein to encourage healing. Example bone inducing materials includebone morphogenetic protein, tricalcium phosphate, hydroxyapatite, andcollagen.

The various elements (guidance elements, screws, screw heads, rods,retention threads, locking assemblies, etc.) may be provided in a rangeof sizes, shapes, strengths, flexibilities, and other physicalcharacteristics to best accommodate individual patients and particularapplications. Other embodiments include combining two or more of theelements mentioned so that the combined elements can be insertedtogether instead of one at a time. For instance a locking assembly thatis attached to a rod or that is placed downwards together with a rodwill save one separate step of placing the locking mechanism after therod is placed. Similarly, a rod that is attached to the second screwhead vertically by a hinge can then be swung down into the guidanceelement and screw head of the first screw after the second screw hasbeen placed. A rod wire will further ensure that the tail end of the rodstays within the guidance element of the first screw. This combinationsaves the separate step of placing the rod into the incision.

While the illustrated guiding elements and accompanying disclosurediscuss the delivery of a rod via the guiding elements, the guidingelements can also be used to deliver guiding tools designed to compress,reduce a spondylolisthesis, and/or provide counter-torque when lockingthe a rod member in place. In addition, various other tools can beprovided to assist in stabilization, such as dynamic stabilization.

FIGS. 23A-23C show how for a three level stabilization the rod 104 canbe guided down by the guidance elements on a first screw head while theguidance elements on a second and third screw head are splayed outwardor bent to open the receiving or encatchment area for the rod to easilyenter. In the conventional case of pedicle screw towers, the rod had tobe precisely inserted through the small opening within each rigid tower.Embodiments of the present invention overcomes this difficulty. It willbe appreciated with multi-level procedures, a single incision may beused for delivery of all of the screws, implants or instruments.Alternatively, multiple incisions may be used as desired, with one ormore of the incisions accommodating screws, implants and instruments formultiple vertebra. For example, as shown in FIGS. 25A-25C, the lowesttwo levels (L5 and 51) share a single incision but the upper two levels(L3 and L4) have separate incisions. Rod retention threads only span theinferior half of the rod and only capture the guidance elements of thelower two vertebrae (L5 and S1). The superior end of the rod is thenpushed through the guidance elements of the upper two vertebrae (middlefigure). Or, a thread that is attached to the superior end of the rodcan be used to pull the rod through the guidance elements of the uppertwo vertebrae. This thread can be introduced in between each set ofguidance elements by a large suture needle that is inserted in oneincision and is pulled out of the next incision in between the guidanceelements.

As shown in FIGS. 24A-24C a refined T-shape tool 108/109 may be used toseparate the guidance elements 103. This gesture prevents them frombecoming tangled (or disentangles them) and opens the space in betweenthem such that a rod can be passed through it to enter the screw head.The horizontal arms 109 of the “T” extend outward perpendicular to thelongitudinal insertion axis 108. These arms 109 may be aligned parallelagainst the main longitudinal body during insertion and removal. Theymay also be inside the main body and deployed from within via telescopicextension or a spring-like mechanism. The end of each horizontal arm 109may be U-shaped, V-shaped, or circular such that a guidance element 103can be retained within it. If the ends are U-shaped or V-shaped theT-shaped tool 108/109 can be disconnected from the guidance element 103easily after spacing by collapsing the arms to realign against thelongitudinal insertion axis 108 or to collapse into the main body. Ifthe ends are a closed loop shape such that the guidance elements 103 arefed through them and trapped within them, the loops should be configuredto open to release them (like a jewelry clasp) after the tool 108/109has performed its function.

FIGS. 31A and 31B illustrate one or more assemblies of telescopingguiding elements in use with vertebrae according to some embodiments.FIG. 31A illustrates an assembly comprising a plurality of telescopicguiding elements 131. The plurality of telescopic guiding elements 131includes an upper guiding element 132, a lower guiding element 133 and amiddle guiding element 138. The lower guiding element 133 of theplurality of telescoping guiding elements 131 is positioned closest tothe pedicle of a vertebra and is wider than the upper guiding element132, which is positioned closer to the incision 200. The incision 200 isat skin level. The telescoping guiding elements may progress from widernear the vertebrae to narrower near the skin. For example, in someembodiments, the lower guiding element 133 includes an internal width ordiameter that is greater than the middle guiding element 138 or upperguiding element 133, thereby allowing the middle guiding element 138 orupper guiding element 133 to “telescope” within the lower guidingelement 133. The telescoping feature allows for adjustment of the heightof the assembly of telescopic guiding elements, which advantageouslyresults in less crowding closer to the incision 200 in order that moreguidance elements from a greater number of vertebrae can fit through asingle incision. In some embodiments, at the skin level incision 200,guidance elements from different vertebrae all converge on one another.Away from the skin level incision 200 and closer to the vertebrae theguidance elements diverge.

As shown in FIG. 31A, the plurality of telescoping guiding elements 131can comprise a plurality of cylindrical tubes that can “telescope”(e.g., slide into and/or relative to one another) and assume variousheights as an assembly. In some embodiments, each of the plurality ofcylindrical tubes can move along a longitudinal axis relative to oneanother. In other embodiments, the plurality of telescoping guidingelements 131 can comprise other shapes as well, includingnon-cylindrical elements. In the illustrated embodiment, the pluralityof telescopic guiding elements 131 include three different tubularmembers; however, different embodiments can include any number oftelescoping members. For example, a plurality of telescoping guidingelements 131 can include only an upper guiding element and a lowerguiding element, or in other cases, more than three telescoping guidingmembers. In addition, each of the telescoping guiding elements can havevarious internal widths or diameters, such that they can each beinserted individually through the single incision. In some embodiments,one or more tubes have a diameter of between about 14 mm and 25 mm andare capable of fitting through an incision of between about 14 mm and 25mm. In one embodiment, edges of the telescopic guiding elements may bechamfered or U-shaped 134 as shown for the upper edge of the uppertelescopic guiding element 132.

As shown in FIG. 31A, one or more extension members 238 can be operablyconnected to the telescoping guiding elements 131. In the illustratedembodiment, the extension members 238 comprise wires or threads operablyattached to the upper guiding element 132. In the event that theplurality of telescoping guiding elements assume a reduced height (e.g.,as shown by the plurality of telescoping guiding elements 131 in FIG.31B positioned below a skin incision), the extension members 238advantageously extend through and outside the incision and allow a userto properly identify the location the plurality of telescoping guidingelements of reduced height. In some embodiments, the extension members238 can also advantageously serve as guiding elements themselves, suchthat rod members or other implants can be guided toward the plurality oftelescoping guiding elements.

FIG. 31B illustrates the use of a first assembly comprising a pluralityof telescopic guiding elements 131 and a second assembly comprising aplurality of telescopic guiding elements 151. The first plurality oftelescopic guiding elements 131 includes an upper guiding element 132, amiddle guiding element 138, and a lower guiding element 133. Extensionmembers 238 in the form of wires extend from the upper guiding element132. Similarly, the second plurality of telescopic guiding elements 151includes an upper guiding element 152, a middle guiding element 158 anda lower guiding element 153. Extension members 258 in the form of wiresextend from the upper guiding element 152. As shown in FIG. 31B, afterthe pedicle screw attached to the telescoping guiding elements 131 isdelivered into a vertebra, the height of the telescoping guidingelements 131 can be reduced so that the upper guiding element 132 ispositioned below the skin incision 200, but the wires 238 extend out ofthe incision 200. This provides room for the pedicle screw attached tothe second telescoping guiding elements 151 to be delivered into thevertebra. As shown in FIG. 31B, the second plurality of telescopicguiding elements 151 can advantageously be inserted into a desiredposition via the same single incision 200, thereby reducing the amountof trauma to a patient compared to other guiding systems that requiremultiple or larger incisions.

FIGS. 32 and 33 illustrate the delivery of a spinal implant in the formof a rod using telescopic guiding elements as discussed above. As shownin FIGS. 32 and 33, with the first set of telescoping guiding elements131 still reduced in height and the second set of telescoping guidingelements 151 extending through the incision 200, a rod 104 or otherimplant can be inserted through the same singular incision as theguidance elements. The rod 104 can be inserted through a center of theplurality of telescopic guiding elements 151. The rod 104 enters throughan opening in an upper guiding element 152 as part of a second guidanceelement assembly attached to a second vertebra and is directed downwardsto a lower guiding element 153 as part of the same first guidanceelement assembly. The lower guiding element 153 has a window 155 thereinconfigured to permit passage of the rod 104 therethrough. A first end ofthe rod 104 is passed through the window 155 of the lower guidingelement 153 of the second assembly of guidance elements and maneuvereduntil it enters a window 135 of a lower telescopic guidance element 133of a first assembly of guidance elements 131 attached to a firstvertebra. The first end of the rod 104 can be guided down the pluralityof telescopic guiding elements 151 until it enters a channel forreceiving it in a first screw head of a first screw in the firstvertebra (as shown in FIG. 32). Then the other (second) end of the rod104 is guided down the window 155 until it enters a channel forreceiving it in a second screw head of a second screw in the secondvertebra (as shown in FIG. 33). As shown in FIG. 33, at this point theheight of the second plurality of telescoping guiding elements 151 maybe reduced such that the uppermost element 152 is below the skinincision, with the wires 258 extending through the incision. Using thewires 238, the height of the first plurality of telescoping guidingelements 131 may be increased to again extend through the skin incision.This first plurality of telescoping guiding elements may then be used todeliver instruments therethrough, for example to delivery a lockingassembly to the pedicle screw. Further extensions and reductions in theheight of the telescoping guiding elements may be employed as desired bythe surgeon in order to perform appropriate procedures on the patient.

While the illustrated embodiments in FIGS. 32 and 33 depict the guidanceof a rod implant down the telescoping guiding elements, the telescopingguiding elements can also help guide non-rod implants, as well aslocking devices (e.g., cap members) and tools for compression,distraction, and various other spinal procedures.

Methods of spinal stabilization using telescoping guiding elements asshown in FIGS. 31A-33 will now be described. Initially, a singleincision 200 is formed in a patient. In some embodiments, the incisioncan be between 0.5 cm and 4 cm, more preferably 3 cm or less or 2 cm orless. A first screw is provided and can be pre-attached via its screwhead to a distal end of an assembly of telescoping guiding elements 131prior to insertion into the patient. A second screw is also provided andcan be pre-attached via its screw head to a distal end of an assembly oftelescoping guiding element 151 prior to insertion into the patient.Each assembly of telescoping guiding elements 131 and 151 can include anupper, middle and lower guiding element, wherein the upper and middleguiding elements can “telescope” or slide relative to the lower guidingelement to adjust the overall height of the assemblies. In addition,each assembly can include one or more extension members 238, 258attached, for example, to the upper guiding elements 132 and 152,respectively.

After forming the incision, the first screw and its accompanyingassembly of telescoping guiding elements 131 can be positioned throughthe incision. The first screw can be placed in a desirable locationadjacent to the vertebrae. Using a screw driver or other tool throughthe assembly of telescoping guiding elements 131, the first screw can befixed to a first vertebra. At this point, the assembly of telescopingguiding elements 131 extend from the first screw through the incision200, as shown in FIG. 31A.

To allow for the insertion of the second screw and its accompanyingassembly of telescoping guiding elements 151 through the same incision200, the assembly of telescoping guiding elements 131 can be reduced inheight so that the upper guiding element 132 is below the incision 200.Contact is maintained with the upper guiding element 132 by using one ormore extension members 238 that are attached to the upper guidingelement 132. The extension members 238 can comprise one or more wires,and extend from the upper guiding element 132 and through the incision200. Using the extension members 238, a surgeon or other user can easilylocate the position of the reduced height assembly of telescopingguiding element 131.

With the height of the assembly of telescoping guiding elements 131reduced such that the upper guiding element 132 is below the incision200, the second screw and its accompanying assembly can be placedthrough the same incision 200. The second screw is fixed to a secondvertebra (e.g., using a screw driver). At this point, the accompanyingassembly of telescoping guiding elements 152 extends from the secondscrew to outside of the incision 200. Like the first assembly, thesecond assembly of telescoping guiding elements 151 can also includeextension members 258 attached to an upper guiding element 152 tothereby maintain contact with the second assembly outside of theincision. As shown in FIG. 31B, the extension members 258 of the secondassembly can criss-cross or intersect the first assembly of telescopingguiding elements 131 and/or its extension members 238 at or near theincision 200.

If desired, additional assemblies of telescoping guiding elements can beintroduced through the same incision. For example, the heights of boththe first assembly of guidance elements 131 and the second assembly ofguidance elements 151 can be reduced below an incision to make way for athird assembly of guidance elements via a similar procedure.

With the first assembly of telescoping guiding elements 131 and secondassembly of telescoping guiding elements 151 in place through the sameincision, a rod member can be delivered. With reference to FIGS. 31B and31C, a rod member 104 can be delivered through the interior of thesecond assembly of telescoping guiding elements 151. The rod isdelivered such that it is turned and angled through a window 155 formedin the second assembly (as shown in FIG. 31C). One end of the rod canthen be optionally delivered through the window 135 formed in the firstassembly. At this point, one end of the rod can be secured into the seatof the second screw head, while the other end of the rod can be securedinto the seat of the first screw head. Locking elements (e.g., capscrews) can then be delivered through each of the telescoping tubes tosecure the rod into the seats of the first screw and second screw. Ifneeded, the heights of each of the assemblies of telescoping guidingelements can be adjusted in order to expose an upper guidance element ofeach of the assemblies above the incision 200 in order to insert thelocking assembly.

Once the rod member 104 is in place, the assemblies of telescopingguiding elements 131, 151 can be decoupled and removed from theirrespective screws. Instruments can be inserted through the telescopingguiding elements to actuate a release mechanism to release thetelescoping guiding elements from the screws. The assemblies oftelescoping guiding elements 131, 151 can be then removed from out ofthe patient and the incision can be closed. The patient can be left toheal. Advantageously, as the procedure only involved a single,relatively small incision, the patient experienced less trauma and canexpect a faster healing time compared to if other conventional methodshad been used.

FIGS. 34A to 34D illustrate embodiments of a hybrid system utilizing atleast one set of non-cylindrical telescoping guiding elements. As shownin FIG. 34A, the telescoping guiding element 300 need not be cylindricalbut can have other shapes. The telescoping guiding element 300 shown inFIG. 34A includes substantially rectangular arms or blades 315 havingsquared edges that provide a channel or pathway for the delivery of arod or other spinal implant therethrough (as shown in FIG. 34D). Theguiding element 300 may include wires 238 as described above. In someembodiments, the height of one or more blades 315 can be adjusted bymoving one part of a blade 315 relative to another. For example, asshown in FIG. 34D, the blade 315 can be adjusted by moving component 315a relative to 315 b, thereby shortening or lengthening the height of theblade 315. Preferably there is a friction mechanism that keeps component315 a fixed at a specific position relative to 315 b. The frictionmechanism can be augmented by flexible teeth that further 315 a fromsliding spontaneously relative to 315 b. The interior of blade component315 a is slightly larger than the interior of blade component 315 b,thereby allowing relative sliding between the two members. Thetelescoping guiding element 300 further includes one or moreindentations or grooves 304 therein that provides a channel or pathwayalong a length thereof to receive a protrusion of a locking assembly,tool, or other element in order to guide it down to a delivered rod.

FIGS. 34B to 34D illustrate the use of telescoping guiding element 300including substantially rectangular blades in combination with anon-telescoping guiding element 310. It will be appreciated that inother embodiments both sets of guiding elements may be telescoping. InFIG. 34B, a telescoping guiding element 300 can be reduced in height tohave short blades 315 and extension members 238 can be used inconjunction to control or extend the length of the telescoping guidingelement. Guiding element 310 may comprise a conventional set of longblades 311 to deliver a rod or other spinal implant to a desiredposition within a channel in a screw head. Thus, in one embodiment, thetelescoping guiding elements may first be delivered with a first screw,and then reduced in height to allow delivery of a second screw having aconventional guiding element.

In FIG. 34C, the telescoping guiding elements 300 can be extended usingwires 238 to criss-cross or overlap with the long blades 311. As shownin FIG. 34C, a rod 304 can be guided and delivered to the screws usingthe blades 315 a, 315 b and 311. With the blades 315 a and 315 bextended, as shown in FIG. 34D, a screw cap locking assembly 119 (asdescribed above) can be delivered to lock the rod 104.

The telescoping guiding elements can have any shape or configuration andstill be within the spirit and scope of the present invention. They maybe cylindrical as shown in FIG. 31A or have straight edges as shown inFIG. 34A. The telescoping guiding elements can also have any number ofsegments or portions that collectively form the telescoping assembly orsystem and still be within the spirit and scope of the presentinvention. As shown in FIG. 31A-33, at least three separate portions ofcylindrical telescoping tubes are visible. As shown in FIG. 34D, atleast two separate portions (315 a and 315 b) of substantiallyrectangular telescoping arms are visible.

Additionally, there are several different variations of the telescopingmechanism all contemplated within the spirit and scope of the presentinvention. FIGS. 32-33 and 34B-34D show the narrowing of the distancebetween one telescoping guiding element from another telescoping guidingelement, as the telescoping guiding elements come closer to the incisionrelative to their positions near the vertebrae.

In addition, within their individual assemblies, the telescoping guidingelements can be configured such that guiding components closer to theincision have a smaller width or diameter relative to guiding componentscloser to the vertebrae. For example, with respect to FIG. 31A, theupper guiding element 132 can have a smaller width or diameter relativeto the lower guiding element 133, such that the upper guiding element132 can be slid into and out of the lower guiding element 133.Alternatively, the telescoping guiding elements can be configured suchthat guiding components closer to the vertebrae can have a smaller widthor diameter relative to guiding components closer to the vertebrae. Forexample, with respect to FIG. 34D, the upper component 315 b of theblade can have slightly larger dimensions relative to lower component315 a of the blade, such that the upper component 315 b can be slid overand around the lower component 315 a.

In the illustrated embodiment in FIG. 34D, the upper telescopingcomponent 315 a closer to an incision rides along the outside of thelower telescoping component 315 b closer to the vertebrae. That is, insome embodiments, telescoping guiding elements closer to the incisionhave a larger dimensions (e.g., widths and diameters) than telescopingguiding elements closer to the vertebrae. In some embodiments, the uppertelescoping component 315 b can be cut-out to receive the lowertelescoping component 315 a closer to the vertebrae. The lowertelescoping component 315 a closer to the vertebrae can be solid filledor hollow (cut-out), and is configured to fit into the upper telescopingcomponent 315 b thereabove.

FIGS. 35A to 35C show another embodiment of guiding elements where atleast some of the guiding elements are removable and reinsertable intothe patient. The illustrated embodiment presents a “hybrid” system of anon-telescoping guiding element 310 and a novel guiding element 300 withremovable and reinsertable components. As shown in FIG. 35A, guidingelement 300 includes upper guiding component 315 a and lower guidingcomponent 315 b. While in one embodiment these components may betelescoping, in another embodiment they may not be. The screw with thesecomponents attached are delivered into a first vertebra. Then, as shownin FIG. 35B, the upper component 315 a can be removed from the incision,leaving the lower component 315 a behind, but attached with wires 238extending through the incision 200. The wires may be attached to thelowermost guide component 315 b, or alternatively may be attached to thescrew as well so that component 315 b may also be removable over thewires. A screw attached to a conventional guiding element such as blades310 may be delivered into a second vertebra, criss-crossing with thewires 238. As shown in FIG. 35C, the upper component 315 a can bereattached to the lower component 315 b as desired, to deliver rod 104or other implants or instruments to the spinal location. In oneembodiment, there may be multiple (e.g., two or more) removable guidecomponents that are slidable along the wire or wires 238, in order toadjust the height of the assembly as desired. Although FIGS. 35A-35Conly illustrate one guide element having removable guide components, itwill be appreciated that there may be multiple such assemblies, one perscrew.

FIGS. 36A to 36C show a hybrid system 400 for rod and implant deliverycombining longer extended blades or arms 415 a with shorter blades, armsor tower 415 b. The shorter blades 415 b can be attached to one or moreguidance wires 238. As shown in FIG. 36A, the longer extended blades 415a and/or the shorter blades 415 b extend from the top of a screw head102. In other words, one side of a screw head 102 or one side of achannel configured to receive a rod within the screw head 102 has thelonger extended blades 415 a and the other side has shorter blades 415b. Both the longer blades 415 a and shorter blades 415 b are used toguide a rod 104 into position into a desired position in the seat of ascrew head 102 of a screw that has been placed in the pedicle portion ofa vertebra. In some embodiments, the longer extended blades 415 a can betelescopingly shortened, while the shorter blades 415 b can betelescopingly extended. While in the illustrated embodiment in FIGS.36A-36C the guidance elements are not telescoping, in other embodiments,telescoping features can also be included. As shown in FIG. 36B, ahybrid assembly comprising a long blade 415 a and a short blade 415 bwith wire 238 attached to a screw head can criss-cross with a similarassembly. The use of a wire 238 as part of the hybrid assembly providesflexibility such that the second assembly with screw head can passthrough the passageway created by the wire 238 and long blade 415 a inthe first assembly. In one embodiment, the long blades or short bladesmay be similar in shape to the guide tabs or the sleeves described inU.S. Publication No. 2009-0234392 A1 and U.S. Pat. No. 7,758,584, theentirety of each of which is hereby incorporated by reference.

In some embodiments, the longer extended blades or arms 415 a may reachall the way to and through the skin level incision or may be connectedto wires that go through the incision. The shorter blades, arms, ortowers 415 b do not extend to and through the skin level incision. Byusing shorter blades 415 b in the hybrid system 400, there is lesscrowding around and at the skin level incision, thereby allowing roomfor additional longer extended blades attached to multiple vertebrae tofit through the same incision. As shown in FIG. 36A, the side on whichthe longer and shorter blades are placed can alternate from one pediclescrew or vertebra to the next, such as described in the above referencedU.S. Publication No. 2009-0234392 A1 and U.S. Pat. No. 7,758,584. Thismay help to provide greater stability overall for a multiple levelstabilization or fusion. For example, on a first lower vertebra thelonger extended blades 415 a may be placed on the lateral side (withshorter blades 415 b on the medial side) while for a second highervertebra the longer extended blades 415 a are on the medial side (withshorter blades 415 b on the lateral side).

In addition to the hybrid systems discussed above, additional hybridsystems that combine any of the guiding elements discussed above arealso possible. For example, a system for rod delivery can include amixture of one blade and one or more wires on a single screw. Anothersystem for rod delivery can include one tube or tower on a first screwand one or more wire or blade combinations on the second screw. Variouscombinations of guiding elements that can be used through a singleincision are possible.

Similar methods as discussed above with respect to FIGS. 31A to 33 arealso applicable to the alternate embodiments of the guiding elementsshown in FIGS. 34A to 36C. Such methods can involve the use of one ormore assemblies of telescoping guiding elements having adjustableheight, whereby one assembly is at a height below an incision and theother assembly is at a height above the incision during use. In someembodiments, the assemblies of telescoping guiding elements are capableof criss-crossing or intersecting. Rod members or other implants can bedelivered down the assemblies of telescoping guiding elements and intoplace into seats of the screw heads.

FIGS. 37A-37D compare the volume of drilled holes and orientations forpedicle screws inserted according to (i) a traditional method along ananteromedial trajectory and (ii) a new method along ananteromediolateral trajectory. FIG. 37(A) shows anterior viewsillustrating drilled hole volumes for a traditional screw on the leftside and a new cortical screw on the right side. FIG. 37(B) showslateral views illustrating drilled hole volumes for a traditional screwon the right side and a new cortical screw on the left side. FIG. 37(C)shows a radiograph of a pedicle screw placed according to the new methodalong an anteromediolateral trajectory with cortical bone placement.FIG. 37(D) shows a radiograph of a pedicle screw placed according to thetraditional method along an anteromedial trajectory.

A more recent method to place screws into the pedicle uses a mediallateral or anteromediolateral trajectory. The apparatus and method ofthe present invention can be used with this new cortical screwtrajectory approach. By using this cortical approach with the presentinvention four screws may be placed for a one level fusion and sixscrews may be placed for a two level fusion all through one smallmidline incision. (See FIG. 38)

A recent study found that these new cortical trajectory screwsdemonstrated a 30% increase in uniaxial yield pullout load relative totraditional pedicle screws, although mixed loading demonstratedequivalency between the two trajectories. The new cortical trajectoryand screw design have equivalent pullout and toggle characteristicscompared with the traditional trajectory pedicle screw, thus confirmingpreliminary clinical evidence. The 30% increase in failure load of thecortical trajectory screw in uniaxial pullout and its juxtaposition tohigher quality bone justify its use in patients with poor trabecularbone quality. (See Santoni, “Cortical bone trajectory for lumbar pediclescrews” in The Spine Journal 9 (2009) 366-373.)

The systems described in the present application can be used to placethese screws to project in the medial lateral or anteromediolateraldirection for improved results in osteoporotic patients. Traditionalscrews project in the anterolateral direction. (See FIGS. 37A-37D). Themediolateral placement of screws allow bilateral screws to be placedthrough a single midline incision. When applied maximally, multi-levelfusions can be performed through a single percutaneous midline incision.

FIGS. 38A and 38B show side and head-on views of a two-level fusion,which involves stabilizing three adjacent vertebral bones spanning twoproblematic disc spaces, with all guidance elements (e.g., wires) on allthree vertebrae fitting through a common single incision at skin level.As shown in the illustrated embodiment, each of the screw heads 102 isoperably connected to one or more guidance elements 103 that can be usedto deliver one or more rods across three adjacent vertebrae. In otherembodiments, rather than using guiding elements comprising wires tostabilize three adjacent vertebral bones, the guiding elements cancomprise any of the telescoping guiding elements described above, aswell as any of the hybrid guiding elements. Advantageously, thetwo-level fusion procedure can be performed using a single, relativelysmall incision through which multiple guiding elements can be inserted.

In addition to cortical screws and pedicle screws, other embodiments ofscrews placed into vertebrae can benefit from the present embodiments.Recent developments in spinal stabilization have popularized spinousprocess fixation. However, the implants such as the X-Stop™ (Medtronic),Aspen™ (Lanx), and Spire™ (Medtronic) devices typically need incisionsof 4-8 cm. Another embodiment of the current invention uses screwsthrough the spinous process that are connected by a rod type connectorto stabilize the spinous process. Bone grafts sized to fit in betweenthe spinous processes allow an inter-spinous process fusion, similar toan inter-vertebral body implant and fusion. The inter-spinous processimplant can also be connected to the rod connector for furtherstabilization. Because the width of the spinous process is typicallythinner than the typical length of pedicle screws and cortical screws,the spinous process screws can be modified to include a wing thatexpands on the other side of the spinous process once the screw travelsthrough the spinous process to the contralateral side. Such a mechanismis similar to the anchors used to secure pictures and hangers ontohollow walls or doors such as Molly bolts. This inter-spinous processstabilization method can also be used in conjunction with a MicrofusionTLIF procedure where an interbody implant, pedicle screws, and aninter-spinous process fusion have all been placed through a single 15-20mm unilateral incision. A further embodiment includes the use of laminarscrews where the screw travels through the lamina. Such laminar screwsare commonly used for C2 fixation. These and other locations forvertebral screws are easily incorporated into the present embodiments inwhich guidance elements allow a connector and locking mechanisms to beimplanted through a single small incision.

Advantageously, the guiding elements described above, including thewires, plurality of wires simulating a “blade” or “tab,” and assembliesof telescoping guiding elements not only provide a minimally invasivemeans to deliver a spinal implant into a patient, but they are alsoeffective at keeping tissue and muscle away from pathways for implant(e.g., rod) travel. In the case of cortical screws, as shown in FIG.38A, the medially positioned incision allows the screw to be placedbeside the spinous process and muscle. In this case only lateral guidingelements are necessary to retract tissue and muscle because the there islittle muscle and tissue medial to the screw.

FIG. 39 shows different views of a telescoping guiding element includinga half-cylinder portion. The telescoping guiding element 500 comprises acylindrical portion 533 having a window 535 and a half-cylindricalportion 532 slidably mated thereto. The distal end of the telescopingguiding element 500 is connected to a screw having a screw head 102 andshaft 101. The telescoping guiding element 500 is configured such thatthe half-cylindrical portion 532 can be slidably mated along the outersurface of the cylindrical portion 533. The half-cylindrical portion 532can move up and down along the outer surface of the cylindrical portion533, thereby allowing for height adjustment of the telescoping guidingelement 500. Other suitable shapes for the upper telescoping portionalso include the guide tabs or sleeves of the above referenced U.S.Publication No. 2009-0234392 A1 and U.S. Pat. No. 7,758,584

FIG. 40 shows different embodiments of the telescoping guiding element500 with the half-cylindrical portion 532. In FIG. 40A, thehalf-cylindrical portion 532 is attached to outside of the bottomguiding element 500. Alternatively the half-cylindrical portion 532 canbe attached to the inside of element 500 thus reducing the diameter ofportion 532 (FIG. 40B). Half-cylindrical portions 532 with differentdiameters allow better intermeshing when two or more half-cylindricalportions meet at a common skin incision. Furthermore, thehalf-cylindrical portions 532 can have proximal tips that are less than(FIG. 40C) or greater than (FIG. 40D) a half cylinder. The variabilityallows better intermeshing between multiple telescoping guiding elementsat the incision. In fact, different embodiments include the proximal endof the guiding element having any shape that partially fills theperimeter of the skin incision including a partial oval, partialrectangle or square, a partial polygon, a partial helix or spiral, apointed or tapered proximal end, or guiding elements that projectproximally as a spiral or helical shape. The guiding element 500 can beused similarly to other telescoping guiding elements discussed above inthat the guiding element 500 can be placed through an incision and thenreduced in height to provide more space to allow additional guidingelements to be placed through the same incision. Once a desired numberof guiding elements are in place through an incision, one or more spinalimplants (e.g., rod members) can be delivered through the guidingelements to assist in vertebral stabilization.

Minimally invasive methods of providing a stabilizing implant across twovertebrae will now be described with respect to FIGS. 41-45. As shown inFIG. 41, an incision 200 is made in a patient. A screw having a screwhead 102 can be pre-affixed to a distal end of a telescoping guidingelement 500 having a half-cylindrical portion 532 and cylindricalportion 533. The telescoping guiding element 500 can be positioned suchthat the screw is fixed into a first vertebra. At this point, thetelescoping guiding element 500 is of an extended length and passes fromthe screw head through the incision 200 (see FIG. 41).

Once the telescoping guiding element 500 is positioned, the height ofthe guiding element 500 can be reduced by sliding the half-cylindricalportion 532 down the body of the cylindrical portion 533, therebyreducing the overall height of the telescoping guiding element 500. Asshown in FIG. 42, the telescoping guiding element 500 is reduced to aheight wherein the top proximal end of the guiding element 500 isapproximately at or below the skin incision 200. By reducing the heightof the guiding assembly 500, this advantageously provides a high amountof space for delivering a second telescoping guiding element 600 throughthe incision 200. Although not shown, wires (such as wire 238) or othermechanisms may be used to maintain contact with the half-cylindricalportion 532.

A second telescoping guiding element 600 having an upperhalf-cylindrical portion 632 and a lower cylindrical portion 633 canthen be delivered through the incision 200. Like the first telescopingguiding element 500, the distal end of the second telescoping guidingelement is fixed to a screw via a screw head 102. As shown from thedifferent perspectives in FIGS. 43 and 44, the half-cylindrical portion532 of the first telescoping guiding element 500 provides plenty of roomfor the second telescoping guiding element 600 to be delivered throughthe same incision 200.

After delivering the second telescoping guiding element 600 through thesame incision 200, the second screw can be affixed to a second vertebralbody. The system now comprises two telescoping guiding elements 500, 600having proximal end portions at or near the incision 200. Thehalf-cylindrical portions 532, 632 of guiding elements each provide achannel through which it is possible to deliver a spinal implant (e.g.,a rod member) therethrough. The second half-cylindrical portion 632 mayalso be slid down to the level of the skin incision 200, as desired. Asshown in FIG. 45, a rod member (not shown) can be guided via theinterior of the half-cylindrical portion 632 down to the cylindricalportion 633. One end of the rod member can pass through the window 655of the second guiding element 600 and can pass into the window 555 ofthe first guiding element. The rod member is now in a position such thata first end can rest on a first seat in the first screw head and asecond end can rest on a second seat in the second screw head, therebyserving as a stabilizing member across two vertebrae.

FIG. 45 shows the half-cylindrical guiding elements at skin level in asuperior-inferior orientation for the elements. Because thehalf-cylindrical guiding elements 532 and 632 can rotate on the lowercylindrical portions 533 and 633, the orientation for the guidingelements at skin level can also be medial-lateral or any orientationreachable by rotating both upper half-cylindrical portions 532 and 632.The embodiment shown in FIG. 45 can also be accomplished withouttelescoping means. By measuring the desired height of thehalf-cylindrical guiding element from the top of the screw head to theincision, fixed and non-telescoping half-cylindrical guiding elementswith the exact measured length can be attached to the top of the screwhead and placed with the screw into the incision. The height of eachhalf-cylindrical guiding element can be measured exactly by a measuringtool that slides over the guide wire used to access the pedicle or otherpart of the vertebrae through which the screw is to be inserted. Byaccounting for the height of the screw head in this measurement, theheight of the guiding element that exactly comes to the incision can bemeasured. In this manner, the embodiment shown in FIGS. 42-45 can beperformed without any telescoping means or adjustment in height.Desirably, the height of the guiding elements is kept at the level ofthe skin incision to minimize interference with other screws and guidingelements.

FIGS. 46A-46D show embodiments of a guiding element 700, 710 havingexpandable blades or tabs. In one embodiment, a blade 700 is attached tothe screw head 102, and a second blade 710 can be separated from blade700 using a retractor mechanism at the proximal ends outside the skinincision. In one embodiment, the two blades 700 and 710 may not becompletely connected, but instead just one blade (e.g., blade 700) isattached to the screw head. In this manner, blade 710 may move freelyand is more like a retractor. A retractor mechanism is used at theproximal end to spread apart, hold, lock and/or collapse the two bladesas necessary. As shown in FIGS. 46B-46D, the blades 710 can be expandedsuch that a channel is created for rod or tool delivery. In someembodiments, it is possible to criss-cross a pair of guiding elements700 at or near an incision to thereby introduce a rod minimallyinvasively. In one embodiment, the individual blades or tabs 710themselves are capable of expanding apart. The two blades 700 and 710may be connected with side connectors like a foldable fan or accordion,such that they can move from a low profile configuration as shown inFIG. 46A to a wider, larger profile configuration in FIG. 46D.

Many of the inventive features discussed above (e.g., providingcriss-crossing guiding elements in the form of wires, blades/tabs, ortelescoping elements) can also be applied to improve existing devices asfeatured in other applications. For example, the fixation system in U.S.Pat. No. 7,758,584 to Bankoski et al. (assigned to Synthes) can beimproved by including telescoping features, which would allow itsmultiple implant holders in the patent to be criss-crossed at or near anincision, thereby reducing the size of the incision. Currently, thelateral implant holder, sleeve, and tissue protection portion in the'584 Patent appear to extend through the skin incision and has noability to telescope to different heights, including at or below theskin surface. Furthermore, the '584 Patent describes the intermeshing ofguiding tubes with helical shaped cutouts. Since the helical cutoutshave a fixed angle, the intermeshing is accomplished only when the angleof the helical cutout matches the lordotic curvature of the spine. Sincethe lordotic angle varies from patient to patient and level to level,the fixed helical cutout is not practically amenable to optimalintermeshing and cannot minimize the skin incision. The fixation systemin U.S. 2009/0234392 to Dziedzic et al. (assigned to DePuy Spine, Inc.)can also be improved by including telescoping features, which wouldsimilarly allow the multiple guide tabs in the publication to becriss-crossed at or near an incision, thereby reducing the size of theincision. U.S. Pat. No. 7,846,093 to Gorek et al. (assigned to K2M,Inc.) can also benefit from telescoping features. Moreover, none ofthese applications apply guiding elements in the form of wires as in thepresent application, which can easily extend through a number of variousangles from a vertebral body to an incision, thereby allowing theguidance elements to intersect at or near an incision with ease andincrease minimal invasiveness. Furthermore, none of these applicationsteaches that intersection of the guiding elements at or near the skinincision permits the smallest incision size by maximizing the overlap ofguiding elements at the incision, nor do they teach a method to inserttwo or more screws through such a small incision without interferencebetween screws and guidance elements. Additionally, the rod and lockingmechanism in each of these applications require visualization of the rodand screw head. In certain embodiments of the present application, therod and locking mechanisms are trapped and confined to fit into thescrew head such that the entire process can be performed percutaneouslywithout needing to look into the incision. This ability affords greaterflexibility, ease, and permits a smaller, possibly the smallest skinincision. Each of the disclosures of the '584 Patent, the '392Publication and the '093 Patent as specified in this paragraph areincorporated by reference in their entireties, and any of the inventivefeatures discussed herein are applicable to these references.

Further, any of the procedures using the guiding elements describedabove can be performed with the assistance of one or more robots. Theuse of robots advantageously provides increased precision and could bevery useful in delivering screws, rods, locking assemblies, and guidingtools down the guiding elements. Robotic assistance can be furtherimproved by endoscopic visualization as well as stereotactic guidance.These tools help to speed up surgical time and reduce the size of theincision towards the theoretical limit of the width of a single screwfor spinal fusions.

The present invention is not limited to the embodiments described above.Various changes and modifications can, of course, be made, withoutdeparting from the scope and spirit of the present invention.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. (canceled)
 2. A system for bone stabilization, comprising: a screwcomprising a screw head, the screw head comprising a first side and asecond side, the first side and the second side opposite each other; anda guiding element configured to extend away from the screw, wherein theguiding element comprises: a first blade configured to engage with thefirst side of the screw head and extend away from the screw, a secondblade configured to engage with the second side of the screw head andextend away from the screw, and wherein the first blade and the secondblade are curved in order to offset the first blade from the oppositesecond blade.
 3. The system of claim 2, wherein the first blade and thesecond blade are curved along a plurality of axes.
 4. The system ofclaim 2, further comprising a spinal fixation element configured to beretained between the first side and the second side of the screw head ofthe screw.
 5. The system of claim 2, wherein the first and second bladesare nondeformable.
 6. The system of claim 2, wherein the first andsecond blades are pre-formed to be curved in order to offset the firstblade from the opposite second blade.
 7. The system of claim 2,comprising: a second screw comprising a screw head, the screw head ofthe second screw comprising a first side and a second side, the firstside and the second side opposite each other; a second guiding elementconfigured to extend away from the second screw, wherein the secondguiding element comprises: a first blade configured to engage with thefirst side of the screw head of the second screw and extend away fromthe second screw, and a second blade configured to engage with thesecond side of the screw head of the second screw and extend away fromthe second screw.
 8. The system of claim 7, wherein the first blade andthe second blade of the second guiding element are curved in order tooffset the first blade of the second guiding element from the oppositesecond blade of the second guiding element.
 9. The system of claim 8,wherein the first blade and the second blade of the second guidingelement are curved along a plurality of axes.
 10. The system of claim 8,wherein the first and second blades of the second guiding element arenondeformable.
 11. The system of claim 8, wherein the first and secondblades of the second guiding element are pre-formed to be curved inorder to offset the first blade from the opposite second blade.
 12. Asystem for bone stabilization, comprising: a first screw comprising afirst screw head, the first screw head comprising a first side and asecond side, the first side and the second side of the first screw headopposite each other; a second screw comprising a second screw head, thesecond screw head comprising a first side and a second side, the firstside and the second side of the second screw head opposite each other; afirst guiding element configured to extend away from the first screw,wherein the first guiding element comprises: a first blade comprising aproximal end and a distal end, the distal end of the first bladeconfigured to engage with the first side of the first screw head andextend away from the first screw, and a second blade comprising aproximal end and a distal end, the distal end of the second bladeconfigured to engage with the second side of the first screw head andextend away from the first screw; a second guiding element configured toextend away from the second screw, wherein the second guiding elementcomprises: a first blade comprising a proximal end and a distal end, thedistal end of the first blade configured to engage with the first sideof the second screw head and extend away from the second screw, and asecond blade comprising a proximal end and a distal end, the distal endof the second blade configured to engage with the second side of thesecond screw head and extend away from the second screw; and wherein afirst distance between the proximal ends of the first blade and thesecond blade of the first guiding element is different than a seconddistance between the proximal ends of the first blade and the secondblade of the second guiding element.
 13. The system of claim 12, whereinthe first distance is greater than the second distance.
 14. The systemof claim 12, wherein the first blade and the second blade of the firstguiding element are curved in order to offset the first blade from theopposite second blade.
 15. The system of claim 14, wherein the firstblade and the second blade of the first guiding element are curved alonga plurality of axes.
 16. The system of claim 12, further comprising aspinal fixation element configured to be retained between the first sideand the second side of the first screw head and between the first sideand the second side of the second screw head.
 17. A method of treatingthe spine, comprising: making an incision in the skin of a patient toprovide access to a spinal location; delivering a first screw throughthe incision and into a first vertebra, the first screw having a firstscrew head comprising a first side and a second opposite side, wherein afirst guiding element is removably attached to the first screw, thefirst guiding element comprising: a first blade removably engaged withthe first side of the first screw, the first blade extending away fromthe first screw, and a second blade removably engaged with the secondside of the first screw, the second blade extending away from the firstscrew; delivering a second screw through the incision and into a secondvertebra, the second screw having a second screw head comprising a firstside and a second opposite side, wherein a second guiding element isremovably attached to the second screw, the second guiding elementcomprising: a first blade removably engaged with the first side of thesecond screw, the first blade extending away from the second screw; anda second blade removably engaged with the second side of the secondscrew, the second blade extending away from the second screw;manipulating one or both of the first guiding element and the secondguiding element to cause the first and second guiding elements tointersect; and delivering a spinal fixation element to the first andsecond screws using one or both of the first guiding element and thesecond guiding element.
 18. The method of claim 17, wherein the firstblade and the second blade of the first guiding element are curved inorder to offset the first blade from the opposite second blade, suchthat when the first and second guiding elements intersect, the first andsecond blades of the second guiding element are positioned between thefirst and second blades of the first guiding element.
 19. The method ofclaim 17, wherein: the first blade comprises a proximal end and a distalend, the distal end of the first blade being removably engaged with thefirst side of the second screw head; the second blade comprises aproximal end and a distal end, the distal end of the second blade beingremovably engaged with the second side of the second screw head; andwherein a first distance between the proximal ends of the first bladeand the second blade of the first guiding element is greater than adistance between a second distance between the proximal ends of thefirst blade and the second blade of the second guiding element.
 20. Themethod of claim 17, further comprising: delivering a screw cap betweenthe first blade and the second blade of the first guiding element tosecure the spinal fixation element into the first screw head above thefirst screw.
 21. The method of claim 17, further comprising: removingthe first blade and the second blade of the first guiding element fromthe first screw; and removing the first blade and the second blade ofthe second guiding element from the second screw.